HP 8620 - problem with the printer or ink system / printhead appears missing

[Frolin]

A couple weeks ago, my HP OfficeJet Pro 8620 printer/scanner, failed with printing.

It started with a  "Printer Failure" message that says...  "There is a problem with the printer or ink system. Turn printer off, then on. If problem persists, contact HP"

I pulled the printhead, did various deep cleanings, from the print fluid thru the ports and the head bottom printhead.  Did this twice.  Did find the Magenta cartridge did leak some in the head, cleaned that out throughly.
Also installed all new print cartridges.
Did the power off and on, no help, same message.
While powered on, unplugged for 60-90 seconds, re-plugged in, same message.
This did not resolve the problem.

So I purchased a new printhead, now I get...  "Missing or Failed Printhead"  and the message was "The printhead appears to be missing, not detected, or incorrectly installed"
Removed the new printhead, cleaned it, reinstalled, same message.

Powered off and on,  and unplugged while powered on,  re-plugged in, same error.
Ordered another printhead and got the same message  .... ?

Tried my original printhead and got the first message.
Almost seems, the new printheads are not 'recognized' and the original is jammed.

...unplugging is not suggested but is given as a reset step in some places.

Tried to contact HP Support but found,  I am a year out of warranty.

Any suggestions, options, things to try,  short of buying another printer ?

[KrazyToad]

@Frolin

Welcome to HP Community

I have gone through your Post and I appreciate all your efforts and expertise in troubleshooting this issue

Please ensure the printer has the latest Firmware. Link: https://support.hp.com/us-en/product/details/hp-officejet-pro-8620-e-all-in-one-printer-series/53676...

If the issue persists then the printer needs to be replaced or serviced. 

Since the printer is out of warranty, I have sent you a private message with the contact details for HP Support

Please check your private message icon on the upper right corner of your HP Forums profile.

Next to your profile Name, you should see a little blue envelope

If the information I've provided was helpful, give us some reinforcement by clicking the "Solution Accepted" on this Post and it will also help other community members with similar issue.