Two possibilities:

• Reinstall Thunderbird from https://www.thunderbird.net/
• Disable Thunderbird access to Mac address book - Mac System Preferences > Security & Privacy > Privacy > Contacts > click the lock to allow changes > uncheck Thunderbird

Let us know results

In the end I installed a completely new version from Mozilla and deleted the old one. Luckily I could choose my previous accounts as defaults. Thank you. Much appreciated.

Thanks for the feedback.

FYI, Thunderbird is not developed by Mozilla. See "Who We Are" at https://www.thunderbird.net/

p.s. what version were you running prior to reinstalling? It might be revealed at help > troubleshooting > update history

Wayne, I have the same problem, but the 2 suggested solutions have not fixed it. I am on version 52.9.1 and don't want to change that version! Removing access to the mac address book did not change anything.

The folder panel on the left doesn't show words anymore, and some other buttons and areas don't show words or clickable fields anymore.

Help please :)

Wayne, I have the same problem, but the 2 suggested solutions have not fixed it. I am on version 52.9.1 and don't want to change that version! Removing access to the mac address book did not change anything.

If safe mode on 52.9.1 didn't help, I don't have a solution that doesn't involve moving to a newer version.

just tried opening in safe mode, it does not help.

Please see https://www.google.com/search?client=firefox-b-1-d&q=%22safe+mode%22+thunderbird

Thanks!

Same thing here. Jörn, did you find a solution for Thunderbird 52.9.1 in Big Sur with the default theme? I also want to stay legacy because of old-style extensions. Some older custom themes make TB work even in Big Sur but make TB look ugly. Example: Nautipolis v.2.0.34.

Reinstall did not work for me. Disabling contacts access did work. Up and running for now.

Reinstall did not work for me. Disabling contacts access did work. Up and running for now.