Had this problem a while back.
Solution ,from Mozilla,was - do not create your account direct into Thunderbird.
Create it in OE ,make sure it works OK,and then import it into T'bird.
It worked for me - hope it does for you.
What is ransomware and how do I protect my PC from WannaCry?
What I learned from my mentor, Oscar-winning VFX supervisor Phil Tippett
Siri vs Google Assistant
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