After deleting all the advised files - still problem. User posted Error Console information. Ensured Thunderbird was installed ok. Repeated the deletion of files. This time advised to start Thunderbird 'Run as Administator' and all fixed. https://support.mozilla.org/en-US/questions/1388962 The error console may show what files could not be accessed as permissions not inherited.
Bug 1789326 Comment 26 Edit History
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After deleting all the advised files - still problem. >folderCache.json folderTree.json virtualFolders.dat session.json xulstore.json also deleted virtualFolders-1.dat User posted Error Console information. Ensured Thunderbird was installed ok. Repeated the deletion of files. This time advised to start Thunderbird 'Run as Administrator' and all fixed. https://support.mozilla.org/en-US/questions/1388962 The error console may show what files could not be accessed as permissions not inherited.