Printer+cartridges+drying+out

If you don't intend to use a printer for a while, or have blocked nozzles, and cleaning cycles refuse to unblock the dried ink in the print head, put a squirt of Windolene in the foam tray under the print head, leave it 24 hours and then run a nozzle check.

Use the clear Windolene and not the one in the pink bottle. 