I've been using Thunderbird for years and have never had this problem. Since the upgrade today, after I run Thunderbird once and close it I can no longer start it up again. I have to reboot or use Task Manager to kill it in order to run it. This is on Windows 11. Please help - not an acceptable workaround for long. Optionally, how do I downgrade to previous version? I should know better than allow automatic upgrades.

Adding a couple images below, when it has started successfully it shows as one of the Apps in Task Manager. When I close it, Thunderbird drops into the Background Processes but doesn't end. I have to kill it here in order to start it again.