Why aren’t my songs playing on iphone

Recently songs haven’t been playing on my iPhone, when I tap on them to play it takes me to the Apple Music subscription page. It’s only happening with a couple of cds I’ve bought and added to iTunes. The most confusing part is that it’s only every second or third song in the album. I really hope this isn’t apples way of getting more people to sign up for Apple Music, some of my music isn’t even on the iTunes Store