Status idle + Test page onl shows top (reddish). Rest is blank.

well ( a deep subject) that is an ink problem as most are if not jams.
a high end Laser jet printer, needs new cartridge I bet.

Most printers have a test page, even from the front panel
google the manual and read how to do that, and does.

first google hit finds the manual in 1second flat. (amazing)
351 page of bliss.

https://cdn.kyostatics.net/dlc/za/documentation/usermanual/fs-3540mfp_fs-3640mfp6.-downloadcenteritem-Single-File.downloadcenteritem.tmp/FS-3540MFP_FS-3640MFP_OG_ENG.pdf


at Printer panel
go to status print page and print status ,see p227
got error messages see page 301

Capillary hole in the cartridge head is still closed, trying to soak in hot water and inflatable slowly then wipe cartridge head with a tissue

Doing the "clean printhead/cartridge nozzles" multiple times would have cleared clogged nozzles. You can also try to manually wipe the cartridge nozzles with a slightly moistened soft cloth. If that still won't help, try to replace your cartridge with a different known working cartridge to determine if your other cartridge is faulty.

Sometimes the cartridge will show "good" when they actually need to be replaced. Try printing a test page, cleaning the ink nozzles, and if the problem persists, replace the ink cartridges.

replace the cyan image unit might go a bad one

Btw, I’m available to help over the phone in case u need at https://www.6ya.com/expert/normanj_7893313f0751935f

the cartrdges contacts are well, the ink it is clogged in the printheads, take out the cartridges, put them in a wet towelwith windows cleaner liquid, just the head height, let rest 12 hours, clean and dry the heads and try to print, sometimes need a second time on liquid. good luck

Hi devi960:
Pages print, but all
colors do not print or
the pages are
completely blank.
One of the print cartridges might be
low or empty.
Run an engine test and see if all four colors print. If
not all colors print, replace one or more of the print cartridges. If the
engine test is successful, replace the formatter.
If the printed pages are completely
blank, the file might have blank
pages.
Check the file to make sure that it does not contain blank pages.
A print cartridge might be low or
empty.
Check the printer control panel for a Supplies Status message,
print a Supplies Status page, or use the embedded Web server
(HP color LaserJet 2500 series printers only) to see the levels
remaining in the print cartridges. Replace any print cartridges that
are low or empty. Messages are not created for non-HP print
cartridges.
If you are using non-HP print
cartridges, one or more print
cartridges are low or empty. The
control panel lights do not indicate
low or empty for non-HP print
cartridges.
Replace one or more of the print cartridges.
Font DIMM might be selected but the
font DIMM is not physically installed in
the printer. (This issue applies only to
HP color LaserJet 2500 series
printers using an Asian-language font
DIMM.)
In the settings for this printer, clear the Font DIMM check box on
the Configure tab if no font DIMM is installed in the printer. Select
the Font DIMM check box only if the font DIMM is physically
installed in the printer. If you think that the font DIMM is installed,
make sure that it is installed correctly.
The paper curls when
exiting the top output
bin.
The paper needs to print to the
straight-through paper path.
Open the rear output door to print to the straight-through paper
path. Remove each sheet as it exits the printer.
The stack was slightly curled when it
was placed in the tray.
Turn the stack over in the tray.
The paper does not meet
specifications.
See the user guide for information about print-media specifications.
If you are printing on light media, the
Type setting might not be correct.
Select Light in the Type is field in the printer driver.

Is the black cartridge full?

I just got done replacing my toner.  You'll need to change toner and most likely all of them. There is no other solution.  I refill mine by buying the bottle toners.  It can be messy and you'll need to take some parts off the cartridge to get to the opening plug and reset the lever so that the printer knows the cartridge is full.  It is cheaper than buying a toner. The cartridge has a life of about three refills.  Anyway hope this answers your problem.

When you print stop the printer half way through then check the image on the opc drum and transfer belt to see if it's complete or not, also you may want to check the aidc sensor (sometimes the cable comes loose). I can e mail you the 2300 series service manual (4.17mb) if you reply with your e mail address