Does problem change if you have done ...

• Start Windows in safe mode with networking enabled - https://support.microsoft.com/en-us/help/12376/windows-10-start-your-pc-in-safe-mode
• Still In Windows safe mode, start Thunderbird in Troubleshoot Mode - https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird

Good assumption - sorry forgot to say running Windows 10 x64 with October patches and Thunderbird en_GB with locales order en-CA/GB/US on POP3/SMTP/S accounts and Import Export Tools NG.

I have an update to TB 128.5esr pending so I will see if I can apply that successfully, or that update also fails, and add info if anything is fixed or changes.

Next weekend before Patch Tuesday, I will apply November patches and other app updates, then reboot into Safe mode with networking, start Thunderbird in Troubleshoot mode, as suggested, and let you know if Thunderbird comes up with email accounts enabled for receiving, or not, or any other changes.

Should I also check the error log before/after process?

Might also solve a SuperNova problem I have had lingering, where filters will only run manually, on a "recently" added account (after SuperNova upgrade) with a "new" private domain+email provider, which appears after Local folders in the accounts list, has an associated GPG key, and does not use the ISP default Thunderbird SMTP account settings.