In the profile that is used by TB, Help/Troubleshooting, Profile Folder, Open Folder, close TB, open the Mail/Local Folders location. Do you see the mbox files, the large files with no extension, named after folders? If you do, delete the .msf files with the same names as the mbox files, restart TB, and see if the Local Folders subfolders appear.

Sorry, I've turned on Hidden Items in my IE window and there are no mbox files in the profile that TB is using. Are there other options?

If there are no mbox files in the Mail/Local Folders location, then there is nothing with any mail content. If you don't have a recent backup, you can copy mbox files from the other profile folder to Mail/Local Folders in the active profile, then restart TB and see if they appear under Local Folders in the Folder Pane.

Thanks sfhowes, but using the local folders from the older profile dated 2017 probably won't work. That version has s short list of subfolders, none which match the current local folder list. Does this mean that the current profile folder was somehow deleted and a new one dated Aug. 5 was created when I launched Thunderbird?

Profiles aren't normally deleted except through manual direction, and if a new profile is created after a program update, it has a different name from the existing profiles. If the mbox files (folders) don't exist on the local computer in some profile folder, I can't explain why they disappeared. Look through all the profiles in ...Roaming/Thunderbird/Profiles.

Thanks sfhowes. The mbox files are not in either of the two profiles.. Also, just noticed that I have nothing prior to June 8 in my Inbox. The Sent files go back to 2020. My Godaddy webmail inbox shows the same.