iPhone won't sync
My iPhone doesn't sync properly with iTunes (12.1). This problem has been going on for months. I have an iPhone 6, but I used to have an iPhone 4S, and it had similar problems. I usually have been able to get it to work eventually, but it keeps recurring. Right now, the sync button in iTunes is greyed out. Rebooting the computer doesn't change the situation. I have a 27" mid-2010 iMac running 10.10.2. I'm wondering whether I should re-install iTunes -- perhaps there is a corruption issue? Is that easy to do?
iPhone 6, iOS 8.2