Windows 10 22H2 couldn't connect to the printer...

[Lotharyx]

Sorry for lack of detail. Not a lot to be found.
Printer hosted by CUPS on Debian Linux, trying to print to it from two different Windows computers. One works; one consistently gives "Windows couldn't connect to the printer" errors.

I have debug logging turned on in cupsd. When the working system sends a print job, and also every minute or two, I see log entries show up in access_log and error_log. When I attempt to add the printer on the non-working system (with the URL https://:631/printers/), nothing appears in either log and the "couldn't connect" message appears within a second or two.

Confoundingly, on the non-working system, I can open the CUPS page in a browser. 🤯 More confoundingly, this very printer worked fine on the non-working system, then just stopped working (coinciding with changing my domain password for Windows, but that didn't bother the system that still works).

It really seems like the non-working system isn't even really trying to connect to the printer. I've tried both http and https URLs and the same thing results: a quick "Windows couldn't connect" and nothing in the CUPS log.

Our IT team wants to charge $beaucoup/hr since they don't manage the CUPS server...so it's up to me to fix it.

What else should I do besides CUPS debug logging? Doesn't seem like a firewall issue, since a web browser can access it...

Complete Windows OS info on nonworking system:
Edition Windows 10 Pro
Version 22H2
Installed on ‎5/‎31/‎2022
OS build 19045.4291
Experience Windows Feature Experience Pack 1000.19056.1000.0

CUPS version 2.22.10 (which is probably very old, but it's an old ARM SBC running it)