Windows 10 File History does not back up ANY files

I've been a long time user of the File History backup system - but recently (I believe while still using Windows 8) it just stopped backing up any files at all. When I manually ask it to run:
  • it appears to run for about 2 minutes,
  • completes, (I can hit "Run Now" again)
  • There are no errors displayed
  • No files are backed up whatsoever
Admittedly I have a bit of a strange system - I was using an internal hard drive with no problems until recently. Yesterday, I tried converting my internal drive into a Virtual Hard Disk following some instructions I found online (can't link as it's my first post on the forum) but that didn't work either. Parts of my libraries are on external hard drives (music, videos, documents and pics), however none of the folders of the libraries are contained on the internal backup drive itself.

On top of this, when I try to alter the WIndows 10 File History settings under "More Options" and add or remove folders, the settings are not saved - the same folders reappear, and the ones I remove return as soon as I close it and return.

What could be going wrong here, do I need to give up on having an internal HD backup and just try one of the externals instead?