Certain songs are gray only in music library

I noticed that some of my songs started turning grey in my music library and whenever i try to play them it says “item not available.” However, whenever i search for the same song on apple music, it lets me play it and the song isn’t gray, but it doesn’t let me download or add the song. I was wondering if anyone had a solution to my problem as to why only some of the songs only in my library are grey but not whenever i search in apple music. Thank you