The subject says most of it.
Canon Pixma iP7250 printer. Stopped working with four out of five ink lights on continuously. Yellow was ok. All other four were empty except the large black one. It had a trickle. Yellow was half full.
Changed all four inks, but those four ink lights are still on continuously. The orange light is giving four flashes. Powered off and on again - still the same. Only my wife does colour printing, I only do occasional b/w on an old HP LJ4, so I don't know why the inks ran out wothout being noticed.
The printer webpage shows all tanks as full - even the half full yellow one. The Mac driver shows 'Information not available' for Supply Levels. The Canon help pages tell you to use a driver 'Utility' tab that does not exist.
Being driven by a Mac running 10.13.6