Sorry if this has been covered ( ran a forum search and nothing came back~please point me to another thread if this re-hashing solved problem).
I recently restored my 3880 that is fitted with the old SEL ink-set and started cleaning and recalibrating. Everything was great until this morning when my PK cart was not recognized and after getting it to recognize the other cartridges became unrecognized.
Until today, I was able to run clean cycles, print a couple of positive test prints and two digital negs (which I did over the past two weeks). Printer was running every few days.
The control chip on the cartridge may have gotten loose or raised.
I suggest taking it up and re-seating the Epson chip, clipping the control chip back on (all carts) and then gently placing them back in the printer 1 by 1 from left to right.
Taping the control chip down tighter to the cartridge (over the raised metal soldering points) also helps it make contact with the Epson chip beneath.