Right, here we go again.
First, I did some maintenance on the Router (turned it off, unplugged all the ethernet inputs, plugged them back in, turned it on again).
Now I SHOULD have tested it there, just to be scientific, but I didn't. I went on to the Router settings and changed the Channel from 'Auto' (allegedly looks for the cleanest local wifi) to number 3.
Then I tried it, with mixed results.
1) On the Macbook, with Ethernet ONLY, no WiFi, prints, and also sees the scanner, implying a LAN-type connection between the machines.
2)With Ethernet OFF, WiFi ON, it prints, but doesn't see the scanner, contradicting 1) a bit.
3) Replaced Ethernet, so now Ethernet AND Wifi - still doesn't see the scanner.
4) Rebooted the CANON, and this time, sees the scanner (suggesting the logjam might be in the Canon, and there ain't no 'clear' or 'reset' button on the thing, of course.
5) However, at this stage MacBook printing starts to 'hang'. Sits in the Print Queue, doing nothing. Printed a sheet through the MacMini, no bother, and that seemed to encourage it, as it was followed by the hanging page from the MacBook.
6) Since then, Macbook sees the scanner every time (although now I'm leaving in Ethernet/Wifi), but printing hangs each time, until I've run another job through the Canon, or even just done a photocopy on it. Then it stops hanging, and runs the page out of the Print Queue.
Apart from being confused (and Patrick, your quote "without really understanding the details or reasons of what they are doing" is absolutely spot on, and no offence taken - I can operate the things, and have done for decades, but I get to a point where ignorance overwhelms me...) it seems to me that the problem might lie with the Canon, rather than with either Mac or the Router. Once it has taken in some 'communication' error, it doesn't just shrug it off, but needs a definite reboot (well, off, then on), to clear its tubes. Make any sense?
Do you think it's worth going back to the original installation CD for the Canon and installing it again? Or are these particular all-in-one Canons prone to being jittery?
(Jake: our MacBook Pro is 17", but it's so old that we can't update to High Sierra, so I join your plea for a new 17" model. Trouble is, the trend seems to be the other way, i.e. smaller and smaller).
Allen.