I just responded to your email, but wanted to include my answer here for others to read + learn from:
After reviewing your order history, I see you purchased the 850ml refill carts for your 7900/9900 printer. As you may be aware, we’ve had a few different cartridge designs for this printer model over the years (in search for the overall best cart), and we actually have a newer 350ml cart than the 850ml ones you have. The 850ml carts are great in many ways, and certainly fit/lock into the printer better than previous carts, but we started having an occasional fit issue with the last shipment, which effects the chip read, and I believe is what you’re experiencing. Unfortunately, the carriage manufacturer wasn’t able to offer us a satisfactory solution, so we continued searching for and testing other carts, which led us to the new 350ml carts we have. I can explain the issue that I believe you’re experiencing with the 850ml carts you have, and hopefully be able to get you happily printing. On top of the cartridge, where the chip is attached, some of the carts have a dip in the plastic, which can make the chip not have a good connection with the printer’s chip sensor. Raising the chip it’s self risks catching on the fragile sensor wires, so isn’t a safe fix. Several people have reported, and we confirmed in our testing, then taking a piece of typing paper about 4x6” and folding it lengthwise in half twice (so it makes a 1x6” strip), then placing it on the bottom of the cartridge bay while sliding the cartridge into place- this raises the cartridge up slightly, which is usually enough to make a good connection between the chip and chip sensor, and the carts/printer work great.
I hope this helps, please let me know if you have further questions or there’s anything else I can help you with.
Best regards~ Dana