Printer bounces between depleted cartridge error and ink system failure

[NadineK]

Hi everyone, I hope to find some help here. I have been searching the internet, including this forum for weeks now, but could not solve my problem. So here it goes:

We bought an Officejet Pro 8600 Plus in the US back in 2013 before we moved to a small Caribbean island. We moved the printer in the unopened packaging to our new home with us and only set it up in the spring of 2016, (as until then our laser printer was working just fine). We used the printer just fine, we print about 300 pages per year (so really not very much). But even though, we don't heavily use it, it kept asking us to replace the cartridges on a regular basis. It wasn't an issue as we had bought quite a few sets at the time and still had spare cartridges.... until the spring of 2019. 
The printer kept insisting, that the black cartridge was empty, even though it was still more than half full. As the printer simply would refuse to work (not even scanning!), we had to buy a replacement cartridge on island.... this is a small island in a developing nation, so original cartridges for this printer weren't available, however, we managed to source a third party ink cartridge for exactly this printer. Not a biggie, we bought XL and it actually worked. All good. Really? No.
So then a few months later in the summer of 2019 (after a firmware update!), it started doing the same with the pink, yellow and cyan cartridge. Said they were empty, even though they were more than half full. So we went back and bought more cartridges. But this time...the printer would NOT accept the 3rd party cartridges. It just kept saying the cartridges are empty and would not print at all.
A bit frustrated, we accepted that. Not using the printer until we went back to my home in Europe this winter and were able to source the original cartridges.

When I set the original cartridges in, the printer did work! And I managed to print 2 or 3 pages. However a few days later, when I needed to print again, the printer said, that ALL the cartridges are empty (this are the original ones, we just paid over100 USD for them (951XL in all 3 colors)!! So then, I take them out and put them back in, follow all the instructions with cleaning the connections, cleaned the printhead, cleaned all the print head connections....everything. Did a soft reset, did a semi-full hard reset (with the set-up cartridges!). Disabled the cartridge count, etc. Nothing helps!!!

Sometimes the printer goes back in to regular menu and accepts the cartridges, but then when I go to print, it either says the realignment doesn't work or the cartridges is empty. Right now, it is stuck into an "ink system failure" error, which it has done so before as well, but I manage to snap it out of it with a few resets.
It all goes back then to the MAIN PROBLEM, that the printer says the cartridges are empty and there is not enough ink in it to print, however, the cartridges are all original and brand new and completely full!

Is there anyway, to a complete, full hard reset? Or re-install the firmware somehow? It just keeps saying that I have the latest firmware.
Anything? I mean, this is a 500 USD printer that we used for less than 1000 pages of printing and it's just not working anymore! I am very frustrated!
Please, help me!

[KrazyToad]

@NadineK

I have gone through your Post and I understand your concerns

Since you have already perform the Semi Full Reset and the issue persists, I suggest you contact HP Support for Service Options

Click on this link - www.hp.com/contacthp/ and select your Country to get the Contact details for HP Support

Thank you

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.