Can you post a screen shot?

I am also having this problem and Resetting the Toolbars & Controls did not work. Attempted multiple times. No luck. I also installed a newly downloaded Thunderbird overtop of the existing TB to see if that would fix it, no dice. I wish I could get it working like you guys did with just Resetting in Safe Mode - but it doesn't work at all.

Also, can't open the "Settings" menu at all. Clicking on doesn't bring anything up.

I can tell it's purely a display issue - as the email is still arriving, and the pop-up appears when mail arrives. Just can't see anything or interact with anything.

Also, I tried a fix from another post saying to change the Theme - but this also didn't change anything.

Very stuck here! Any other suggestions?

When I couldn't see my messages I did a Help>Troubleshoot Mode and it got something up. Still not happy about the threading but they also posted a change about on how to turn it off https://support.mozilla.org/en-US/kb/message-threading-thunderbird#thunderbird:win10:tb102 Just don't know if that will stay working. I love the volunteer group but some of the volunteers are the young folks who modify things for use on cell phones and it's screwing things up for those who use desktop and like it the way it's been.