Thanks for the additional information, and for letting me know your results after disabling the printer's chip sensors.
Based on your results with the chip sensor off, it sounds like these four chips may be not be working correctly, because the printer is indicating a connection with the sensors and chips by working with the sensors disabled (with the sensors disabled, the carts still NEED chips attached, and the sensors still need to have contact with the chips, but the chips don't have to be for the exact color position, or even printer model- for example, you can use a same size/shape chip for a different printer model, and it will work as long as the printer's sensors are turned off).
The 4000, 7600/9600 refill cartridge chips generally work well, but they're getting to be older printer models, so the cartridge and chips designs have stayed the same for the past few years. We still have a good working 7600 here, but I haven't used/touched Epson carts for this model in years, but believe I remember the chips can't be used once they're removed from Epson carts. We can send you four replacement chips, but I'm not not positive they'll correct your problem. I think the best solution is for you to get the two remaining refill carts, and use them with the printer's chip sensors turned off. You can remove and use the remaining ink in your Epson MK and LM carts in the refill carts, and it's fine to physically mix with ConeColor ink (others have done this to avoid wasting their remaining Epson ink, and reported great results).
Please let me know if you'd like me to send the chips, if you have further questions, or there's anything else I can help you with.
Best regards~ Dana