I'm sorry to hear you're experiencing some issues with our refillable carts in your 7900, but am here to help!
Please answer a few questions to help me get a better understanding of your situation in order to resolve your issue and quickly get you back to happily printing.
1. Do you currently have the full set of refillable carts filled with InkThrift ink installed in your 7900 printer?
2. Did you remove air and prime cartridge exit channels with ink using the syringe and small plastic priming tip, syringe only, or a different method/tool?
3. After installing the refillable carts, is your printer's pressurization pump turning on more frequently than when the Epson carts were installed?
4. Please remove the LLK refillable cartridge in question, and examine the cartridge carefully- is the exit channel filled with ink? Is any ink in the plastic body of the cart (outside the ink bag)?
5. Are all other colors fully printing on the nozzle check?
6. Is LLK fully printing on the nozzle check, then completely drops out while printing an image? If so, does it return easily after a regular cleaning cycle or two?
7. Please open the front cover of your printer and examine the length of ink lines inside- are they all filled with ink, or is there any air inside?
8. What ink/carts were previously installed in this printer prior to installing our refillable carts and InkThrift ink?
9. Did you completely or partially fill the carts for the first time, before installing and doing "several power clean cycles"?
10. About how many power clean cycles have you done since installing the refillable carts?
Let me know answers to the questions above, if you have questions or observations that may be helpful for fixing your issue, or if there's anything else I can help you with.
Best regards~ Dana