Welcome to the Forum!!
CTA reads the contents in "c:/users/public/public documents/reallusion" folder
The "Template" folder after that is the Reallusion side of props in your software
The "Custom" folder is the stuff you made / saved.
If your CTA directory is showing empty - it's because it's not looking at that folder, or nothing is installed in them. you may have erased them, relocated them, and you could probably do a search for *.ctActor file in your system to locate where they may be.
If the files are already in that folder and cta is not seeing them, then thats a local issue of your system not allowing the software to read the drive for security reasons, some firewalls with software protection can do that and limit access to any of your softwares / like a sandbox - or maybe even a bad install, because that's where the software is supposed to read since there is no way to alter that ( that i know of! )
I hope there's a solution somewhere in my rambling that helps! lol