My main 'Profile' in T-Bird start up not there

Does profile folder "Three" still exist in folder "Profiles" in .....\AppData\Roaming\Thunderbird\Profiles\ ? The way to verify: in Thunderbird go to Help > Troubleshoot Information > Profiles > about:profiles ....

Unfortunately no

Go back to Help > Troubleshoot Information > Profiles > about:profiles .... Click on Open Folder in one of the profiles: this will open the selected profile in your file explorer. From there go one step higher in the folder hierarchy to the folder "Profiles" and make a screen shot of its contents. Now go still one step higher to the folder Thunderbird which contains a file "profiles.ini" Open this file in a text editor and make a screen shot of its contents

OK got screen shot of the profiles.ini files - do you want to see that??

In order to help you I would like to see the screen shot with the contents of the "profiles.ini" file as well as a screen shot of the "Profiles" folder.

OK - Two screen shots attached

I cannot see a "Profile Three" neither in Profiles nor in profiles.ini You seem to use profile "new User" and/or "Profile Two". There is a "profile-one" in "Profiles" but it is not included in profiles.ini Actually when you start Thunderbird it opens the profile manager window. Please show a screen shot of the profile manager window (see image).

Attached. As you will see there are three Profiles, usually there were four, with Profile Three the lowest, which the one I used all of the time. It's just not there as of this morning.. (The one listed 'Profile - backup', was originally 'New User', but I currently am using that to at least to keep my own emails coming in - I have about 10 others that will have to be reinstalled!)