MP470 printer displays "Print head is not installed" while both heads are there.

[psh]

Have a MP470 printer. Color cartridge was clogged then refilled. After cartridge is put back, it displays "Print head is not installed. Install print head". Does it mean the cartridge is damaged, or the circuit inside printer has problem?

[overswing2000]

Mine won't work either.  How to fix it????????????????????????