Officejet Pro L7780 All-In-One resets - HP Officejet Pro L7780 All-In-One InkJet Printer

SOURCE: hp officejet pro l7780

Run the cleaning tool before you print a test page.

SOURCE: how do i clean the printheads on a hp officejet

hp printers have a utility program that cleans and purges the printer heads. Go to HP on your startup menu and look through the options....mine is located in the "hp solutions center".

It has an option for purging the printer heads.

SOURCE: generic black ink cartridge not printing on hp

You should take it back and exchange it or read on below.

Most modern cartridges have an ink level chip built on to them.
Should the level drop below 25% then most of these chips lock up and will not reset.
Re-filling them will have no effect
If you are lucky you should be able to find either a resetter around on the internet
OR
Even better empty cartridges that never need to be reset.

The second option is my preference

I realise these are not for your specific printer but there are others listed on both those sites as well

SOURCE: Won't recognize black cartridge on hp officejet

Ok what you need to do is powerdown the printer the pull all ink out of the printer power it on without in then power it down again and replace the cartridges. If this doesnt work go into the control panels and select the color of the ink as only B&W and print a test page

SOURCE: Hp officejet pro L7780

I just did the full resetting, hold # + 9 while is on (is what i did) and i unplug the power cord just one is back of the printer, and released for a while to connect again power cord, so when printer star back on, i hold again # + 9 for a 15 seconds, and power off for a moment, later push the power bottom and start a blue screen with FULL RVRAM something like that, leave the printer , is gonne make alignments and so on , so after 10-15 minutes AWSOME , factory reset setting, GOOD LUCK