A question on behalf of my Swiss neighbour
She has a MacBook Pro (Retina, 15-inch, Mid 2015) running Sierra, and a Canon 7550 printer (MG7500 series).
WiFi router is configured on Macbook (browsing works fine).
The printer (Canon 7550) is configured on the MacBook, with the correct print driver version installed and a little green circle showing beside it's name (suggesting the installation is good).
The printer IP address is configured (listed) on the WiFi router.
Nevertheless, every time a print job is started, we get the message: in German: "Drucken - Der Drucker reagiert nicht" (English equivalent: "Print: The printer is not responding").
Despite a superficially correct end-to-end configuration, the Mac doesn't seem to "see" the Canon 7550.
It also fails to "see" the printer using a direct USB cable connection, and using Airprint.
Strange is that my neighbour went to a friend with her MacBook, and could print to her neighbour's Canon printer with no problem.
We've deleted and (in all but results) correctly reconfigured everything quite a few times - to no effect.
Would be grateful for a couple of further troubleshooting suggestions or tweaks.