Where is the main inner paper tray that it says needs emptying so i can print?

Make sure that you have tray 1 set for the correct paper type. Leaving the paper type as unknown will result in very slow printing as the printer will assume that it might be printing on heavy media, envelopes or the like.

LED Blinking in Orange/Green:

2 times: No paper. (ASF) [1000]; Set the paper in the ASF, and press the Resume/Cancel button.No CD-R tray. [1001]*1; Set the CD-R tray, and press the Resume/Cancel button.
No paper in the cassette. [1003]; Set the paper in the cassette, and press the Resume/Cancel button.

3 times: Paper jam. [1300]; Remove the jammed paper, and press the Resume/Cancel button.
Paper jam in the under guide. [1304]
Paper jam in the rear guide.[1303]
Front door closed. [1250]; Open the paper output tray.

4 times: No ink.[1601 / 1611 / 1612 / 1613]; Replace the empty ink tank(s), or press the Resume/Cancel button. Pressing the Resume/Cancelbutton will exit the error without ink tank replacement, however, ink may run out during printing.

5 times: The print head is not installed [1401], or it is not properly installed (EEPROM data of the print head is faulty) [1403 /1405]. Install the print head properly, and close the access cover. Or, with the print head installed, turn the printer off and on.

6 times: Inner cover open. [1841]*2; Close the inner cover, and press the Resume/Cancel button.
Inner cover open (during printing on paper). [1846]*2; Close the inner cover, and press the Resume/Cancel button.
CD-R tray guide closed (during CD-R printing).[1850 / 1855]*1; Open the CD-R tray guide, set the
CD-R tray properly, and press the Resume/Cancel button.
CD-R tray guide open (during printing to paper). [1851 /1856]*1; Close the CD-R tray guide, and press the Resume/Cancel button.

7 times:No CD-R or DVD-R. [1002] After setting a CD-R or DVD-R in the tray, set the tray in the tray guide, and press the Resume/Cancel button.

8 times: Warning: The waste ink absorber becomes almost full (approx. 95% of the maximum capacity). [1700]; Pressing the Resume/Cancel button will exit the error, and enable printing. The service call error, indicating the waste ink absorber is full, is likely to occur soon.
In repair servicing, replace the bottom case unit (QM2-1249), or the ink absorbers (QC1-4222 / 4223 / 4224 / 4263 / 4264 / 4864).

9 times: The connected digital camera or digital video camera does not support Camera Direct Printing. [2001]; After removing the cable between the camera and the printer, press the Resume/Cancel button, and
re-connect the cable.

10 times: Automatic duplex printing cannot be performed (paper size not supported). [1310]; Press the Resume/Cancel button to eject the paper being used at error occurrence. Printing will resume from on the front side of the next page.

11 times: Failed in automatic print head alignment. [2500]; Press the Resume/Cancel button, and after confirming the following, perform print head alignment again: - Set an appropriate type and size of paper (plain paper, A4 or letter). - Check that the nozzle check pattern is properly printed (all ink ejected, no faint printing). - Protect the paper output slot from exposure to excessive light.
Access cover open. [1200]; Close the access cover.



LED Blinking in Orange and Green Alternately, or Lit in Orange:

2 times: Carriage error [5100]
3 times: Paper feed error [6000]
4 times: Purge unit error [5C00]
5 times: ASF (cam) sensor error [5700]
6 times: Internal temperature error [5400]
7 times: Waste ink absorber full [5B00]
8 times: Print head temperature rise error [5200]
9 times: EEPROM error [6800]
11 times: Carriage lift mechanism error [5110]
12 times: AP position error [6A00]
13 times: Paper feed position error [6B00]
14 times: Paper feed cam sensor error [6B10]
15 times: USB Host VBUS overcurrent [9000]
16 times: Valve sensor error [6C00]
17 times: Motor driver error [6D00]
20 times: Other hardware error [6500]
Continuous alternate blinking: rom error

LED Blinking in Orange:

2 times: No paper. (ASF) [1000]; Set the paper in the ASF, and press the Resume/Cancel button.No CD-R tray. [1001]*1; Set the CD-R tray, and press the Resume/Cancel button.
No paper in the cassette. [1003]; Set the paper in the cassette, and press the Resume/Cancel button.

3 times: Paper jam. [1300]; Remove the jammed paper, and press the Resume/Cancel button.
Paper jam in the under guide. [1304]
Paper jam in the rear guide.[1303]
Front door closed. [1250]; Open the paper output tray.

4 times: No ink.[1601 / 1611 / 1612 / 1613]; Replace the empty ink tank(s), or press the Resume/Cancel button. Pressing the Resume/Cancelbutton will exit the error without ink tank replacement, however, ink may run out during printing.

5 times: The print head is not installed [1401], or it is not properly installed (EEPROM data of the print head is faulty) [1403 /1405]. Install the print head properly, and close the access cover. Or, with the print head installed, turn the printer off and on.

6 times: Inner cover open. [1841]*2; Close the inner cover, and press the Resume/Cancel button.
Inner cover open (during printing on paper). [1846]*2; Close the inner cover, and press the Resume/Cancel button.
CD-R tray guide closed (during CD-R printing).[1850 / 1855]*1; Open the CD-R tray guide, set the
CD-R tray properly, and press the Resume/Cancel button.
CD-R tray guide open (during printing to paper). [1851 /1856]*1; Close the CD-R tray guide, and press the Resume/Cancel button.

7 times:No CD-R or DVD-R. [1002] After setting a CD-R or DVD-R in the tray, set the tray in the tray guide, and press the Resume/Cancel button.

8 times: Warning: The waste ink absorber becomes almost full (approx. 95% of the maximum capacity). [1700]; Pressing the Resume/Cancel button will exit the error, and enable printing. The service call error, indicating the waste ink absorber is full, is likely to occur soon.
In repair servicing, replace the bottom case unit (QM2-1249), or the ink absorbers (QC1-4222 / 4223 / 4224 / 4263 / 4264 / 4864).

9 times: The connected digital camera or digital video camera does not support Camera Direct Printing. [2001]; After removing the cable between the camera and the printer, press the Resume/Cancel button, and
re-connect the cable.

10 times: Automatic duplex printing cannot be performed (paper size not supported). [1310]; Press the Resume/Cancel button to eject the paper being used at error occurrence. Printing will resume from on the front side of the next page.

11 times: Failed in automatic print head alignment. [2500]; Press the Resume/Cancel button, and after confirming the following, perform print head alignment again: - Set an appropriate type and size of paper (plain paper, A4 or letter). - Check that the nozzle check pattern is properly printed (all ink ejected, no faint printing). - Protect the paper output slot from exposure to excessive light.
Access cover open. [1200]; Close the access cover.



LED Blinking in Orange and Green Alternately, or Lit in Orange:

2 times: Carriage error [5100]
3 times: Paper feed error [6000]
4 times: Purge unit error [5C00]
5 times: ASF (cam) sensor error [5700]
6 times: Internal temperature error [5400]
7 times: Waste ink absorber full [5B00]
8 times: Print head temperature rise error [5200]
9 times: EEPROM error [6800]
11 times: Carriage lift mechanism error [5110]
12 times: AP position error [6A00]
13 times: Paper feed position error [6B00]
14 times: Paper feed cam sensor error [6B10]
15 times: USB Host VBUS overcurrent [9000]
16 times: Valve sensor error [6C00]
17 times: Motor driver error [6D00]
20 times: Other hardware error [6500]
Continuous alternate blinking: rom error

Hi You have a small paper jam in the front of your machine,
remove all the trays and the toners have a look under the machine in the place of tray 2 you will see a slot that the paper should feed in to. Fold a sheet of A4 in 1/2 lengthways push it in to the slot and with luck it will come out in the machine, holding on to both ends work the paper along the slot moving it up and down until your paper jam come out
if this is useful please rate me.

Look at the tray 1 feed roller with paper in the tray.
Make sure that it is spinning.
If it is spinning, clean it with a damp lint free cloth.
Pull out tray 2 while you try to print from tray 1. Again make sure that the roller is spinning.
If it isn't spinning you have a problem that could be major.

13.05.00 HP CP3505N
Problem Solve. Same error. Generally either a real or phanton jam from the paper tray or manual feed tray.
SOMETIMES the manual feed would work but always one corner on the paper turned down when printed.
Remove toner cartridges and bottom paper tray
Turn printer on its back. The black plastic flap (about 9" long) that hangs down a small amount (near the white main feed roller) had one end most likely the wrong side of the small metal rollers above it.
This flap should hang about vertical. One end of it is most likely the wrong side of the small mostly metal roller above it. Each End of this flap should be about mid way between the two smaller metal rollers.
WITH CARE take a timber skewer and carefully encourage this flap back so that both ends are in the correct place

check the paper type and the paper size from the printer menu, if it is ok then you will try to check the paper sensor on tray 2

No, it won't let you print

there's something wrong with the paper sensor

Well... here it is :

The POWER Lamp Flashes Orange An error has occurred in the printer. The number of flashes indicates the type of error, as outlined below. Check the cause and take the appropriate action.
When a printer error occurs, the POWER lamp flashes. The number of flashes indicates the type of error that has occurred. Count the flashes and take the appropriate action to correct the error.
Two flashes: Printer is out of paper /Paper does not feed
Reload paper to the sheet feeder or cassette and press the RESUME button.
Three flashes: Paper jam/Paper output tray is closed
If paper is jammed, remove the jammed paper, reload paper in the printer, and then press the RESUME button. If the paper output tray is closed, open it.
See Paper Jams
Four flashes: Empty ink tank
Press the RESUME button to resume printing with an empty ink tank. Replace it with a new ink tank immediately after the printing. It may damage the printer if you continue printing with an empty ink tank.
Five flashes: Print head not installed/Print head not installed correctly/Print head is defective
Install the Print Head. If the Print Head is already installed, remove the Print Head and check the electrical contacts for foreign matter, then reinstall.
After reinstalling the Print Head, you may need to realign it.
If this error still remains, the Print Head may be damaged. Contact a Canon service representative.
Six flashes: Inner cover error
To print on paper:
Close the inner cover. Then press the RESUME button to start printing.
Do not move or close the inner cover during printing. It may damage the printer.
Seven flashes: The CD-R or DVD-R is not set on the CD-R tray
Reset the CD-R tray feeder with a CD-R tray containing a CD-R or DVD-R, and then press the RESUME button. Printing will resume.
This function only works with models that support CD-R printing.
Eight flashes: Waste ink absorber almost full
The printer has a built-in waste ink absorber for the ink used during print head cleaning. Eight flashes indicates that the waste ink absorber is nearly full. Press the RESUME button to cancel the error so you can continue printing. Before the waste ink absorber becomes completely full, contact a Canon service representative.
Important
Canon recommends that you call for service as soon as this error occurs. Once the waste ink absorber becomes completely full, printing will no longer be possible.
Nine flashes: A specified period of time has lapsed without receiving no response from the digital camera / The digital camera or digital video camcorder connected is not compatible with this printer
Disconnect the camera cable, press the printer's RESUME button and reconnect the cable.
If the error is still not solved, there is a possibility that you are using a digital camera or digital video camcorder that is not supported by this printer. Use a digital camera or digital video camcorder compatible with this printer.
Ten Flashes: Cannot print on both sides of the page
The size of paper may not be compatible with automatic duplex printing. For information on the size of paper compatible with auto duplex printing, see "Automatically Printing on Both Sides of the Page." Pressing the RESUME button will discharge the paper, and restart printing from the front side of the next paper. The reverse side will not be printed when an error occurs.
Eleven flashes: Cannot perform automatic print head alignment correctly
Possible causes are as follows:
A4 or Letter-sized paper is not loaded on the sheet feeder.
Ink has run out or ink tanks are not installed correctly.
See Ensure that the ink tank is installed properly.
Ink level is low.
Print Head nozzles are clogged.
Press the RESUME button.
For information on how to print a nozzle check pattern, see "Printing the Nozzle Check Pattern."
The paper output slot has been exposed to a strong light source preventing correct print head alignment.
Press the RESUME button to resolve the error. Align the printer so the paper output slot will not be exposed directly to a strong light source.
After carrying out the above measures, if the problem continues after aligning the print head again, press the RESUME button to resolve the error, and then perform manual print head alignment. For details on manual print head alignment, see "Aligning the Print Head."
POWER lamp flashes alternate green and orange:
An error that requires contacting a Canon service representative may have occurred.
Disconnect the printer cable from the printer, and then turn the printer off and unplug the printer from the power supply. Plug the printer back in and turn the printer back on after leaving it for a while.
If the problem remains, contact a Canon service representative.