The calibre database file must be on a file system that supports locking. In some cases if you want your library on a network drive because you do not have enough local storage, you can make it work by keeping the database file local and putting the actual book files on the network drive. But you still need a one-to-one match between a single database file and a single set of library files.
You might want to look into using the calibre content server if you need to access books from multiple locations.
https://manual.calibre-ebook.com/server.html