There are some greyed out tracks removed for ownership disputes or removals, and some may click through to another album, where a version of the track occurs, due to licensing sources conflicting and prior interests.

I recently had an example where a song I own was released on an Australian Daniel O' Donnell compilation CD and streaming/download album, 'Irish Eyes'. However, when you click on the track, it diverts to the same recording supplied by another record company, on the album 'From the Heart', and that source gets the audited play.