The majority of my music in my library won't play.

After transferring music from my old pc to my new mac, it would not play unless I selected a song individually, and no songs would appear in 'up next.' The only songs that will appear in 'up next' when I shuffle the music are songs that I purchased after I purchased this mac. Also when I add the songs to a playlist, they are grey and faded looking, as if they aren't downloaded. But they are downloaded. I had trouble with home sharing when first attempting to transfer my songs. But the songs are on my computer and I can play them if selected. How do I fix this so the music is fully able to play?