Additionally, I turned off the computer and re-launched Thunderbird, that resulted in the same error message. Darryl

How are you creating your backup? Thunderbird has no native support for it.

I use MozBackup (pcv files). Since the initial questions I was able to restore the accounts with on exception that I wanted to ask. I am able to receive both IMAP and POP3, however when I reply or forward two issues occur, Thunderbird freezes and the content in the body is not there. Do you have any suggestions to eliminate these two issues? Many thanks

Some issues here. 1. Mozbackup is no longer supported by the author and it has significant bugs. Use with extreme caution, you might not be able to restore with it.

2. Freezing and no content are probably both the same cause. Your anti virus. When you reply a temp file is created past support issues have highlighted that some anti virus product are so slow that the temp file is not "released" for Thunderbird to use in a timely manner and results in a blank email body. The workaround it t create an exception in your anti virus product for the file nsmail.tmp in your computers temp directory.

Kaspersky Avast and McAfee have all been known to play this game.

Oh, and the import export tools add-on has a backup. I have not used it, but at least it is supported. https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/

Thanks Matt, I really appreciate the help. Darryl

Hi Matt: I wanted to get back to you on how I was able to fix "no response" when trying to reply or forward a message. I deleted ver. 60.0 and installed 58.2 (or a version close to that number). Everything now works using Win 10. Before I did this step I deactivated Defender and the issues were still present. Thought you would like to know.

Now I just need to figure out how to get Google calendar listed under Tools. Have a good day, Darryl