That may mean that, for whatever reason, thunderbird had problems with your profile, so it created a new one. Your old proflle contents are likely still there, but in a different profile. If you click help>troubleshootinginformation, scroll down to 'profile folder' and click 'open folder' you will be in the profile. with mouse click the link in File Explorer to go back one folder so that you are in the Profiles folder. Click there to enter profiles folder and there will probably be two or more profiles. Click into each and then the Imapmail folder and Mail folders to see if your accounts are there. That profile would also have your addressbook. You can attempt to reactivate it by clicking help>troubleshootinginformation, scroll down this time to 'Profiles' and click 'about:profiles, click 'create profile' button in upper left, click next, enter a short name to identify the profile, then click the choose button to locate and select that profile.