Then I'd uninstall and reinstall Thunderbird itself. I believe you are asked whether you wish to retain your account information when you do this, but it's been ages since I have.
The latest versions of Tbird and the add-on have worked as per usual on my machines where I have both.
Brian - Windows 10 Pro, 64-Bit, Version 2004, Build 19041
It’s hard waking up and realizing it’s not always black and white.
~ Kelley Boorn