Does the solution in this topic work?

https://support.mozilla.org/en-US/questions/1292704

This solved my problem on my computer however I tried the same fix on my wife's computer and for some reason the profile isn't showing up in the about:profiles section on her computer. I even went so far as to uninstall and reinstall the latest version of Thunderbird but still the profile isn't showing up? Any suggestions on how to fix this problem on her computer? Her computer is also an HP all in one with windows 10.

And thanks you so much for responding so quickly. Thus far it's been several hours of frustration and worry over losing all those e mails and folders. I tried everything listed and nothing seemed to work. Your suggestion was the first on to direct me to the about profiles section.

Thanks again and hope you have another suggestion for my other computer. Don Weingarten

There's no single method to fix a lost profile, but try this: about:profiles, create a new profile, name it, then Choose folder... and browse to the profile folder that didn't show up.

I tried that and couldn't find the profile listed on my wife's computer. Is it possible for me to copy the profile from my computer onto a CD and then use that copy for my wife's computer? Also, are there any files that need to be deleted prior to uploading the profile on my second computer?

Are you saying there are no profile folders on your wife's computer in this location:

C:\Users\username\AppData\Roaming\Thunderbird\Profiles

You can copy your profile folder into ...\Profiles, then follow the steps in my previous reply.

If there's already a profile folder, named e.g. xxxxx.default-release, which has no account data, you can delete its contents and copy in the contents of your profile folder.

I looked for the profile following the link you provided and also by going in through windows file program. The only profile I can find on the wife's computer is the one I set up today. I did delete the default profiles after I made sure the new profile would still work properly. I can't find anything related to C:\Users\username\AppData\Roaming\Thunderbird\Profiles nor does the computer recognize the command ending with check the spelling.....lol

I guess I'm going to have to resort to copying the profile on my computer onto a CD then downloading onto my second computer and hope that it works. If not, I'll figure something else or she won't have the folders and emails on her computer, which isn't the end of the world in my way of thinking. :-)

Thanks for you help thus far.