Songs I imported from CDs are greyed out in my library on Apple Music. Why can't I play them?

Over the years I imported tonnes of music from CDs into my iTunes but now Apple Music shows them but they can't play. This is on MacBook Air and iPhone, both only a couple of years old and still well able to update etc. I've tried all the basics suggested like resyncing, signing out and in, restarting etc etc but nothing works. I own all this music and so am not sure why I can't access it anymore.