Resolved on my Windows 10 Pro system by backing up then manually editing the following file to remove all references to Inspirata:
C:\Users\<username>\AppData\Roaming\Presonus\Studio One 5\x64\Plugins-en.settings
The plugin entry should, but in my case did not, contain a List section containing info about the actual plugin.
After making this change, restarting Studio One 5 caused the plugin to be rescanned.
The entry was then written correctly to the settings file, and the plugin is now showing up as expected in Studio One 5.