OK, taking a lot of suggestions here, that is good. Thank you.

Getting into engineering mode in the good Zumo will allow it to show up in updater. So that is a positive sign.

Still no joy with the bad unit. With the magnet, going through the multiple ways to get into pre-boot, still can't get it to show up in updater.

And with the multiple ways, I can't even get re-boot to show on the good Zumo.

Sorry to be such a pain!