If you open Help/Troubleshooting Information, click about:profiles, are there multiple profiles shown, and is the one with your data, xxxxxx.default, actually named as the Default profile?

I appreciate the response. Yes, under AppData/Roaming/Thunderbird/Profiles there is only one folder named xxxxxx.default. Then under that is all the various folders and files. I have screen shots below.

With just a single, unrecognized profile, it appears you have the common case of the disappearing profile:

http://kb.mozillazine.org/Recovering_a_profile_that_suddenly_disappeared

You are awesome. That was it. There was a prefs-1 file and a prefs. Somehow a copy was created that was the one with the correct info in it. I just renamed it to the prefs and bingo, everything is back. Thank you.

After updating to Thunderbird 68.2.3 (32 bit) I lost the ability to access a second profile via Windows 10 pro (64 bit). I could not previously get the profiles working correctly in this OS, but was able to access the second site via Run "Thunderbird.exe" -p. This had to be entered any time I wanted to access this second profile - and it worked well. Now I cannot use the same method, even though the profile appears available as usual in File Explorer and profile setup. What has changed and how can I get access again to my second profile?

TB has to be closed before starting Profile Manager. Check Task Manager for any hidden instances of the exe. Or, manage profiles from Help/Troubleshooting, click about:profiles.

TB was closed and saw no open .exe files in Task Mgr. Access to second profile was lost after updating two or three days ago to TB 68.2.2. I believe there were several version updates that I allowed.

This has always been a problem in Win 10 Pro. I can still see the Profile contents for both Profiles in Win File Explorer and they both reflect that they have the same content as earlier. I have always been able to sign into the first Profile. Had to use RUN and "Thunderbird.exe" -p to sign into second Profile. Now using that method, I get no response from Profile Mgr. Also tried offline and could not get access to second Profile.

Profile Manager appears here when I press Windows key+R and type

thunderbird.exe -p

No quotation marks.

I tried with no quotation marks and Profile Mgr came up, as it did with quotation marks. When I entered either of the profiles there was no response when I used the Profile Mgr. I waited for over 5 minutes. This time, I could not find a thunderbird.exe location in File Explorer that would allow me to open my first profile. The files were present, but they all opened the Profile Mgr. I could usually open this site by using OPEN or Administrator to open the first profile after getting locked up in the Profile Mgr. I was forced to reboot. Then the original desktop icon opened the first Profile. I still have the server settings for the setup of the second site, and I have the Profile file available. Can I reestablish this site using a new TB setup using these settings - without jeopardizing access to the first Profile?

I have no problem getting to the Profile Mgr. I have trouble starting either Profile from there. I have used Thunderbird for nearly 20 years in Windows, Windows 95, Windows 98, Vista, Windows XP and Windows 7. Windows 10 has been a problem.

I can't say why you can't launch TB in the existing profiles, so I suggest you create a new profile with Profile Manager, and add your accounts. Address Books and other data can be added from the old profile if necessary.

http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Thunderbird

I've just had an "upgrade" to 68.4.2 fail to recognise an existing profile (xxxxxxxx.default) and create a new one instead (xxxxxxxx.default-release).

It gave no reason why it did this, and there's no information on the resulting "create an email account" screen that suggests that old email data is still there, just in a different profile.

Surely at the "create accounts because there are none in the profile" stage it would make sense to say "... but there are other profiles with accounts in them"?

(for completeness the solution was, as already noted above, to stop Thunderbird, run from the command like with the "-p" flag, choose the old profile and continue).