A family of Microsoft relational database management systems designed for ease of use.
It's dangerous to store working copies of Access accdbs in OneDrive or DropBox. These locations don't work the way Access wants to work. You can get away with it for a while, as you did before this incident.
That's in addition to the problem you now confront, though.
When Access closed unexpectedly, it appears to have left behind the locking file, the one with the same name as your database, but with the .laccdb extension. The .laccdb file controls users' ability to work with a shared accdb. Look for, and delete, the .laccdb file for this one. Only that file, of course.
Then, I would urge you to reconsider working with an accdb on OneDrive or Dropbox, etc., at all. The problem there is that the ability share the accdb with others is blocked when you store those files in such locations. And that runs counter to what Access is designed for. If you truly never share the accdb, I suppose you can continue to get away with it, but as a matter of principle, I think it's not a wise choice.