When you say TB does not load what behavior does it show? Can you identify the process starting in process manager? Is it set to start minimized?

Make sure you are not running anti-virus software or other software that would block TB process from running.

To identify the issue: You can try referencing this article Thunderbird Crashes

or

after you try launching the TB instance, check out Window's Event Viewer (Launch via start menu)-> Windows Logs -> Application. You might be able to locate the TB error code when it encounters an error loading.

Let us know if this was helpful.

Thank you, Brisu, your comment is appreciated. However, when I try to load event viewer I get a message saying that the snap-in is defective. Nor will it permit me to copy the complex "reason" for the problem and transfer it here. I do attach a screenshot of what shows up first on the screen.

I did uninstall TB entirely and downloaded and installed a new version. That worked for a day. Now (Monday) I have the same problem. TB will simply not load. I've tried to load it from the start menu, the task bar, and the desktop and nothing works.

The only AV I have is what comes with Windows 10: i.e., Defender, etc. I'm not familiar with Process Manager. Where can I find that? I do not know whether TB is set to start minimized.

Nor will TB start in safe mode. I hold down the shift key and try to start TB but I get the same non-reaction I've gotten before. Further, I have no add-ons in TB. I do have add-ons in Firefox. Would those somehow affect TB?

I look forward to hearing from you.

I found the problem. It was a program called FileSize put out by a group called MindGems. I uninstalled it and rebooted and TB came up fine. I've put in a bug report with MindGems. Thanks for your help!

Sorry that I couldn't be of more help, and I am glad that you found a way to get TB working. Enjoy!

Cheers!