Cannot access personal music library in Music app on Mac

i've stored a ton of my personal cds (not from itunes) onto my Mac in order to dump cds and rely on computer and iphone. It loaded onto MUSIC. I've been able to access those just fine...until today. Now I'm getting message like this:

This is an image of the "home" page showing my music, etc...not Apple Music/iTunes . But, as i said, i cannot access now.

PLEASE help me find my stuff. Without access, years and years worth of music are gone!

[Edited by Moderator]