The printer won't recognise an ink cartridge
Take it out and look at the contacts. An orange strip left on a new cartridge causes this constantly, and so does a fingerprint on the contact pad. Wipe it with a dry lint-free cloth, never a wet one, and push the cartridge in until it clicks properly. If it's a refilled or third-party cartridge, the printer may be refusing the chip rather than failing to read the ink level.