Thanks for the additional information Keith.
There are two similar errors, please specify the exact wording of the message your printer is displaying "NO ink cartridge, install cartridge" or "Ink cartridge error, install cartridge"?
From what you explain, there are a few things that raise concern or questions with me.
1. It sounds to me that you didn't shake your ink cartridges prior to reinstalling them into your printer, after it sat with PiezoFlush for the past year. Installing old, settled ink will not give you good results, and we always instruct to shake ink cartridges to maintain in-suspension pigment for correct and consistent output.
2. After reviewing your order history, I see you have only purchased five individual refillable carts from us for the 7800/9800 printer model (which was earlier this month), and prior to than haven't purchased anything since early 2008, which was the last time you purchased Piezography Selenium ink and refillable carts for a 4000 or 7600/9600 printer model. Where did you get the other 7800/9800 carts you're using (both the three carts to go with the five you bought from us to complete the set, and other set of carts you're mentioning), or are you trying to use the 7600/9600 carts in your 7800/9800 printer?
3. If you're installing the 7600/9600 carts into your 7800/9800 printer, this could certainly cause damage and errors.
4. If you have carts that you got with the printer or elsewhere, but are correct for your printer model, and your printer is displaying the "NO cartridge" error, then I suspect you may have a damaged chip sensor- though it would be extremely unlikely that two of the new refill carts you just installed have the same problem at the same time... Depending on the history of this printer, and the condition aside from the cartridge errors, it's worth fixing the printer (depending on your technical skill and comfort level, this is something you may be able to do yourself).
Please clarify so I can try to help.
Thanks and best regards~ Dana