Thunderbird checks for POP email on only one of two almost-identical accounts
I have two email accounts set up as POP mail servers that I want Thunderbird v. 128.1.0esr (64-bit) to check. Until recently they both worked fine. Now while one of them continues to work, mail for the other is never downloaded. Comparing the Thunderbird Server Settings for the two accounts, they appear to be identical except for User Name and MessageStorage/Local Directory.
Even more confusing, I have identical accounts on both a laptop and a desktop computer. I get the problem with the laptop (above), but *not* with the desktop, where I have Thunderbird v. 102.15.1 installed!
Is there some setting I'm overlooking?