Go into iTunes, click on your iPhone, click on the "Ringtones" tab, and make sure that "Sync Ringtones" is checked and the "All ringtones" radio back is selected.
Mine wouldn't either, all you have to do is check the second box to manually select which ringtones you want to sync (all of them?) and then it should sync them
Go into iTunes, click on your iPhone, click on the "Ringtones" tab, and make sure that "Sync Ringtones" is checked and the "All ringtones" radio back is selected.