Hmmm... CC is not seeing the metadata.db file, so something else is going on. To help further we need a CC debug log. Instructions for sending one to us are here:
Calibre Companion FAQ - How do I get help?. Please erase the multipie.co.uk email address.
BTW: I assume that when you tap on your library in CC you see all the folders for the authors.
Is this Onedrive account special in any way, such as some kind of shared business account?