HP and Canon Printers used to work, now don't show up in the printer list.

[bkdamkr]

My iMac no longer sees my HP and Canon printers but several other devices, all on the same network, continue to work fine.  I know there was a thread about this four years ago but apparently in Apple Land, "that was then and this is now".  I.e, nothing discussed in that thread worked and several things weren't applicable now.

Here is a bunch more info that should answer the usual questions and provide more detail. 

Background notes:

1) My iMac is running MacOS Catalina 10.15.7

2) I do not know if the problem began when 10.15.7 was automatically installed or not.

3) I print wirelessly from  iMac, a non-Mac laptop, and several iPads and iPhones.

4) Only the iMac has the problem I describe, the printer(s) continue to work perfectly from the other devices.

Here's what happened.  Until very recently, my HP and Canon Printers worked perfectly fine with my iMac, and several other devices. Then about a week ago, I tried to print on the HP. Nothing happened at the printer and the print queue on my iMac said the printer was Offline. The Printer list in System Preferences also showed it as Offline.  I tried the Canon printer next with the same results.  I've since gone through all of the possible troubleshooting steps and fixes I can find to no avail.  When I finally reset the iMac's printing system, both printers vanished from the System Preferences list.  None of my applications that print see the printers either.  Even several versions and rounds or the all-purpose computer fix (turning things off and back on) made any difference.

I tried using HPSmart, it didn't see the printer. I deleted the application, downloaded and installed it again - same result.  I tried to get there from other HP and non-HP set up protocols, but none saw the printer. I downloaded what is purported to be the latest firmware from HP, but it won't install.  I get a message saying that it can't be installed because it's not the latest version.

Has anyone encountered this?  Is this something that everyone knows, except me, and has already been solved?  Will installing MacOS Big Sur fix the problem?  I am currently making the switch and the banner says that there is about 1 day remaining in the download process.

Thaniks

Brian