What do you mean by 'and Microsoft created the test environment' ?

Did you simply create a new computer User Account and called it Test? Did you install Thunderbird from the 'Windows App Store' at some point?

Please tell me if you see a profile in this location: C:\Users\username\AppData\Local\packages\MozillaThunderbird.MZLA_h5892qc0xkpca\LocalCache\Roaming\Thunderbird\Profiles/<profile name>

If yes, post image showing the 'profile name' in that location. Then click on the 'ImapMail' folder and post an image showing all it's contents.

If you did not install Thunderbird from Windows App Store then please try this:

Make sure you have logged on to use the User Account called Test. Exit Thunderbird now if it's running.

• In windows search type : %Appdata% - see image as guide
• Select : %Appdata% file folder
• Select : 'Roaming' folder
• Select : 'Thunderbird' folder
• Select 'Profiles' folder to see profile name folder
• Select 'rm7ha0fz.default-release' folder to see contents

In 'View' - Make sure you have selected the option 'File name extensions'.

You say there is no 'prefs.js' without a number which seems very odd. Please double check it really does not exist.

Assuming it does not exist. The file 'prefs-4.js' was the last one to be used. At this point we do not know how much information that file contains. It contains all the data about mail accounts. Let's see what it's got.

• Rename 'prefs-4.js' to say 'prefs.js' - basically remove the -4

Start Thunderbird.

How many mail accounts display in Folder Pane and in Account Settings?