A possibility is that something (maybe an antivirus?) is preventing thunderbird from updating the prefs.js file, which is the one that stores that information. you can get to your profile by clicking help>troubleshootinginformation, scroll down to 'profile folder' and click 'open folder' . You are now in the profile. EXIT thunderbird. Look for prefs.js. if you see other files, such as prefs-1.js, prefs-2.js, etc., that is an indicator. These are simple text files and can be read with Notepad. Starting with the one with highest number, browse to see if it contains all of your accounts. If so, move the other similarly-named files elsewhere as backup (in case you picked the wrong one) and rename this one to prefs.js and restart thunderbird. AND, thank you for your donation.

Hello, Here is the message I get when I want to open the file in question. I would like to point out that I have been using Bitdefender Total Security for several months. Best regards. F. P

Feature: Antivirus

Bitdefender has placed a threat in quarantine. File name: C:\Users\FredPc-Maison\AppData\Roaming\Thunderbird\Profiles\zq5else3.default-esr\prefs.js. We recommend that you perform a system scan to verify that your system is healthy.

The prefs.js file is simple text. That appears to be where the problem is. Bitdefender has it in quarantine, which prevents thunderbird from updating the settings. All I can do is suggest you remove prefs.js from quarantine and set bitdefender to ignore email activity.