About all I could recommend at this point -- if you haven't already tried that -- is to completely remove Thunderbird and reinstall it. I would try
eopkg rm --purge thunderbird, which should not affect anything in your home folder. Then reinstall it.
If that doesn't work for you, you may need to update your repository and install again with the
And if it still doesn't work, I'm afraid I'm out of ideas. Good luck with it!