Cannon MP 640 Printer not responding/connected

Hi!

I have a Canon MP 640 printer which I use infrequently.

I use wireless or ethernet connection.

First time I got the error message " Printer not responding/connected" I solved the problem by cleaning the printerhead in water.
This helped for a while, but the problem has reappeared, and cannot be fixed as first time.

Printing from a SD card works however allthough colors are a bit less intensive.

I assume the problem is infrequent use of an ink printer, so buying a new printer would probably just postphone the problem.

Any hints available??

Best regards

Ole