If the old computer is available, I suggest starting over. It sounds like you may have created the profile while Thunderbird was running. What version of Thunderbird was on old computer?

Hi David, The version I have is 102.5.1. So Maybe doing this without the app on? I don't know if I've done that yet. Worth a try! -M

ver 102 can also create profile copy with tools>export if profile wasn't over 2 gig.

David, Got it to work. I had 1.8 gigs in a local archive folder (now deleted) Copied updated Profile folder to new computer. I also changed the newly loaded profile folder to match the original folder name then changed the old folder to a different name. In Troubleshooting app link I set the updated link as default and opened in new browser. I suspect the excessive amount of archived files was the problem.

It's has all the correct folders and files now. -M