SpamSieve Plugin not viewable in Mail 13.0 (3601.0.10)

Recently I sent my MacBook Pro into Apple for repair. When I sent it in Catalina was installed and SpamSieve was fully functional. When I received the Mac back, it was wiped clean and Mojave was reinstalled. I upgraded to Catalina and then restored my system from TimeMachine. Since that time, SpamSieve has not worked at all.

The main symptom is that from the Mail:Preferences:General:Plugins, there is no plugin visible.

I have performed the instructions at https://c-command.com/spamsieve/help/enabling-and-updating-t several times with no benefit.

I really like the product and it drives me crazy with all the spam without it. How can I get it running again?

Please see Delete the DataVaults Folder.