Libraries not available in SLM or Halion

Hi all
After a brief mounting point issue (which was quickly solved) with my external drive which houses my Steinberg libraries, my libraries are appearing as unavailable ( :no_entry: ) in Halion 7 and are not appearing at all in Steinberg Licensing Manager. I have double checked that the Library default location is correct, have verified that the files are indeed on the drive, shut down/restarted several times, ejected and remounted the drive - nothing happens.

My feeling is that the “index” needs to be rebuilt or something like that - any ideas?

Thanks for your input!

EDIT: Right-click/Handle missing library in Halion does nothing at all

EDIT 2: Deleting mediabay3.db and reopening Halion does not resolve the problem. The only libraries appearing in SLM are the Groove Agent packs
It might be important noting that I was using the Halion trial until earlier this week, when I purchased a license. The :no_entry: symbols is what you normally see when a library has been installed but isn’t licensed or activated. I check, and the Halion license is indeed activated.

Edit 3: it’s not just the libraries that can’t be loaded. Trying to build a new wavetable synth it seems that all of the wavetables are missing too - the dropdown list is empty!

I’m updating this with a new reply - I’ve been focused on Halion but now see that NONE of the instrument/preset libraries are available for any of Steinberg’s products. Only my User presets are available, and they’re not properly functioning because it seems that instrument assets are not available. The files are however all definitely in their respective folders.

Someone elsewhere suggested reinstalling MediaBay, but I can’t see where or how to do this. Apparently it’s a standalone installer available on the Steinberg website but I can’t see it.
Someone else in a different thread mentioned using the “Deep Scan” tool? I can’t see any such tools in Cubase or the Library Manager.

Any ideas, please?