My iPhone 4S won't sync music?

I lost my first 4s to water damage and when I got my new one I restored it with a back up from a week earlier. Everything seemed fine until I tried to open my music. It says that there's no content.

On iTunes it says that there's 6 gigs or whatever of music and if I click the "on this iPhone" it shows all the songs but they are greyed out.

I have tried syncing it without music then syncing with music. I haw tried closing and reopening iTunes. I have tried restarting the computer with the device still plugged in.

Same problem

Try plugging it in again.