If the scanner software is 32-bit, sending a file through TB won't work unless TB is 32-bit. W7 users may also have to install a Visual Studio library. But if it worked before with TB 32-bit, I suspect the problem is 64-bit TB. Uninstall 64-bit and install 68.3.1 32-bit, set TB as the default during setup, then restart the computer. There's no significant performance gain with 64-bit TB.

I am using the Thunderbird uninstaller. Do I delete all the files after it has uninstalled? I did a MozBackup before I started.

Thanks for your help.

I think I answered my own question. If I delete all the files, fresh install of 32 bit and then restore my backup, that will restore my profile and all my data. Am I correct?

Simply uninstall Thunderbird do not remove data if it is offered as an option. When Thunderbird is reinstalled your profile should remain intact.

This is the second time this week I have heard of someone using mozbackup. it is 8 years and many many versions of Thunderbird and a number of windows since that product was updated. You use it as your own risk, as per the product author, and every year the risk gets greater.

Thanks for the heads up Matt.

Problem solved, thanks Matt and sfhowes.