I think either the files are corrupted or thunderbird does not have access to those files (owner changed when you have migrated from windows 7 to windows 10).

For file corrupted you might try like an user mentioned on this area: The reason the server specs kept reverting to what I had originally no matter what I did was because the pref.js file had become corrupted. I first renamed the existing file and then closed Thunderbird and when I reopened it, a new pref.js file had been created. Thereafter the changes that I made to the server for accessing new emails was retained. It turned out that the popstate.dat file was also corrupted. I renamed the file and when I started Thunderbird again, a new file had been created and the duplicate email problem was resolved

• • • those files mentioned above are on your profile: %APPDATA%\Thunderbird\Profiles\xxxxxxxx.default\ ****

For owner issue - you should search on google how to take ownership of some folders on windows 10. Though, if it's a new installation of the operating system (w10) I will rather install a fresh copy of it - but that's another discussion.

Hi thanks for the reply

After some tests we realized that the problem is due to the antivirus software, Kaspersky endpoint security. completely uninstalling the antivirus the problem does not arise, if instead it is only disabled, for some reason thunderbird does not work. This led us astray and initially ruled out that the motive was kaspersky. We are now in contact with kaspersky support to resolve. in case of particular details I will attach it in the post in order to help if someone happens in the same situation.

Andrea