DIAGNOSIS The chip on the new cartridge isn't making contact or isn't being read properly. This happens a lot with third-party or refilled cartridges, but can even occur with genuine Epson ones.
FIX Power the printer off. Remove the problematic cartridge. Look at the copper chip contacts on the back of the cartridge and the corresponding pins inside the printer. Gently wipe both with a dry cotton swab to remove any dust or ink smudge. Reinsert the cartridge firmly until you feel it click into place. Power on.
IF THAT DIDN'T WORK Try the cartridge in a different slot. If the error follows the cartridge, it's likely a faulty chip. If the error stays in the original slot, there might be a bent pin in the printer's carriage. Inspect it carefully with a flashlight.
HEADS UP Using non-Epson cartridges can sometimes trigger this, and firmware updates from Epson are known to block some third-party chips. You may have to seek out a different 'compatible' brand or bite the bullet on OEM ink.