I've never seen this before. Google AI suggests ...

The "SEC_ERROR_OCSP_FUTURE_RESPONSE" error in Firefox, Thunderbird, or other Mozilla-based applications typically indicates a problem with your system's date and time settings. The error occurs because the browser is trying to verify a website's certificate using Online Certificate Status Protocol (OCSP), and the system clock is set to a time before the certificate's validity period.

As a workaround to get you going again turn of OCSP check in Thunderbird Settings. At the top right of the Thunderbird window, click the menu button ≡ > Settings Type 'ocsp' into the search field at the top. Uncheck the option 'Query OCSP responder servers to confirm the current validity of certificates'. Then check your computer's date and time settings.

Thank you for the reply. The error corrected itself about 5 minutes after I made the query. I suspect it was caused by my cpu clock battery. The PC is cold booted every day, however I was in hospital for a week, and in bed for another week, so it probably drained the battery. I also just noticed my system time is off by 3 hours and a day behind. So I need to change the battery. Today my boot showed some error on POST but it was too quick to re-boot to see what it was. And T'bird loaded my mail from the server with no problem. So I am good to go.

jgb