After a recent Windows 10 update, TweakxFSDS ceased to function. Deleting the intermediate files in the FSDS folder, all those preceded by an underscore, resolves the issue. Do this prior to compiling the FSDS code into a model. Then run Tweak as usual.

This apparently was an issue with a previous version of Tweak, but then was resolved, I think, because prior to the Win 10 update, it was working fine.

I moved the FSDS folder out of the program folder.

I also run FSDS and Tweak in compatibility mode for Win XP, and run them as the administrator.

Hope this helps someone.