Problem - Thunderbird Gmail Norton

[king1]

check your date and time are correct, that could affect things as well...

But every time I have struck this problem it is inevitably Norton or some other AV causing the issue. IDK maybe you need to use the Norton Removal tool to get it out completely
https://support.norton.com/sp/en/us/home.../v60392881

The important thing is to make sure Norton is out of the picture and continue troubleshooting from there ie keep peeling back the layers so to speak...