SMB connection to Windows 7 PC shows 0 items

Greetings.

I've got an iPhone 13 Pro, just updated to iOS 15.3.1. I had been able to connect to and browse various Windows 7 PCs that have multiple shares (set to Everyone, so I could write to them as well), but suddenly there are no files visible. I don't get an error when connecting, just note that says "0 items" and "Read-Only" at the bottom of where the shared folders should be.

Interestingly, if I connect to servers (PCs) to which I had not previously connected, it works, either as Guest or Registered user (not sure why one works as Guest but the other requires username and password).

I don't see a way to delete/forget the servers in the list in the iOS Files app. Perhaps deleting them and reconnecting would help, but at this point I'm stumped.

TIA.