My iTunes can't synch music to my iPhone?

My iTunes DOES recognize my iPhone and it's literally connected to my computer with the USB. When I try synching, it says synching successfully completed. But my iPhone doesn't have my music synched. I even tried restarting my phone, deleting my music from my phone, resetting the settings, and reinstalling itunes. I don't understand. Either that or maybe it was the recent itunes update I downloaded on january 22. Need help!

Restore it. Make sure your phone is up to date. Try different cable.