Thank you for your reply.
I have turned the printer off and on and that did not make a difference.
Here is process that lead up to my issue:
I printed one photo with no problem.
I printed a second photo and noticed I had no deep black.
I ran a nozzle check and there was no output from PK head.
I did a Head Cleaning and the same. No output from the PK head.
At this point, I received the error message that the cartridge was not recognized.
I did a transition to the matte black cartridge to see if it was working. The Head check showed it was fine.
When I tried to go back to the PK cartridge I got the error message again.
I put in an Epson PK cartridge and was able to transition back to Photo Black.
I put the CISS PK cartridge back in and still received the error message that the cartridge is not recognized.
The printer is on a surge protector.
Please let me know when the P600 back up chips are available.
Ocassionally, I get the error message on other cartridges, but when I take out the cover pin and replace it, the error message usually goes away. Sometimes I have had to tell the printer to proceed with the non-Epson cartridge.
Thank you very much for your assistance with this. The service from Inkjetmall has been outstanding in the 10 years I have been a customer. I have recommend you to several members of my Camera club and photographic associates.
Have a great day.