I'm trying to move music from my Mac, latest Sierra, to my iPhone 7 Plus using iTunes. The two will connect and see each other but after moving about two albums the entire process stops working, any music moved to the iPhone is then greyed out on the iPhone. The message iTunes is "Waiting For Sync To Start" and it does not start. If I shut both down and reconnect it will then update the greyed out music but then after about two more album transfers the problem starts again. Appreciate your help.