I have a thumbdrive with all my music and also the two MB playlists I use: a 5 star rating list and a no star rating list. (and all of this is on my Android 10 phone too, where I use GMM).
Anyway, I opened my MB to do some manual rating work and found that all the songs with no star won't play on MB, in fact I've somehow, in my futzing, seemed to have removed almost 4,000 unrated songs from MB ... GOOD GRIEF!. After futzing around and not finding a solution I have concluded that I might need to reload all the songs onto the computer via Windows explorer and the thumbdrive, along with a clean version of MB (I have version 3.4.7792). But how do I get those VERY IMPORTANT ratings moved back into MB?
Here are my library settings: perhaps they reveal my stupidity in a way that can be solved: https://imgur.com/xaALhbP