There is a hidden folder which survives reinstallation
C:\Users\YourNameHere\AppData\Roaming\audacity
it contains the files “pluginregistry.cfg” & “pluginsettings.cfg”,
if you rename* those, (to say “pluginregistry-old.cfg”), then restart Audacity,
then you should obtain a fresh start with plugin effects.
[* rename is preferable to delete: gives you the option to revert]