Complain to Yahoo. https://support.mozilla.org/en-US/questions/1205706#answer-1079122 And join the crowd. https://forums.yahoo.net/t5/Account-security/CLIENTBUG-SELECT-command-is-not-valid-in-this-state/td-p/300162

HI. I started having this problem yesterday, but I can still access my emails nad send emails if I go direct to my internet/email provider, Rogers (Canad). I tried all the fixes I found on the Thunderbird support forum (little older responses) but none worked. So I did online chat with Rogers which uses Yahoo for their mail system. I sent them the entire error message, explaining that I've been using Thunderbird with their system for years with no problem. They said to check with Thunderbird, and also sent me a link to do a new "Application Password" for it (Thunderbird). That link was "www.rogers.com/customer/support/article/email-setup"setup" . I haven't tried it yet. If this works I'll let you know.