Do you mean Thunderbird updated and now the Folder Pane is empty - it looks all blank ?

I yes:

Error console is here: 'Tools' > 'Developer Tools' > 'Error Console' Open the 'Error Console' Post an image showing the contents of the Error Console.

Try this first: After posting the image showing contents of Error Console...

• 'Tools' > 'Developer tools' > 'Error Console'
• Clear the error console then close that window.

• Menu icon > Help > More TRoubleshooting Information
• Under 'Application Basics' about half way down is 'Profile Folders' - click on 'Open Folder'

It opens a new window showing the contents of the 'profile name' folder.

• Exit Thunderbird now this is important.

delete the following files - note some files may not have been created

• folderCache.json
• folderTree.json
• virtualFolders.dat
• virtualFolders-1.dat
• session.json
• xulstore.json

This time I need you to start Thunderbird using 'Run as Administrator' - this is important.

• Right click on the Thunderbird shortcut icon and select 'Run as Administrator'

If this fails:

• 'Tools' > 'Developer tools' > 'Error Console'
• Post image of Error Console