Itunes not working on iMac

Hi, I have updated to iTunes 12.5.1.21 today on my iMac and now it won't let me play the songs that i have in my library. It only seems to be letting me play songs that I have actually downloaded.

I am an Apple music subscriber, have tried signing in and out of iTunes - same problem. Restarted several times and checked the App store for updates nothing seems to be working.

All i get when i try to play a song is a solid blue line across the top where the music time length is and for some reason iTunes directs me to the 'Browse' tab with a blank screen. Any help on this one or are Apple servers having some problems? thanks Simon