IPod won't sync music?

Yesterday, my iPod appeared with no music on it. It went into recovery mode and I had to bring it to someone else's computer to get them to restore it, because error 6 kept popping up on my computer. Now my iPod is not in recovery mode and is back to how it was when I bought it. It has the most recent software version, I have not done anything unusual with it, and it is not jailbroken. On iTunes it says that it has all of my music on it, but the iPod says there is 'no content'. I have tried both manual sync and auto-sync, but neither of them will get the music to display. No errors come up when I try to put the music on the iPod, it just doesn't register as being there on the device itself.