I’ll get straight to the point, I’ve found some ringtones that do not have both a Name and an Artist listed for the ringtone won’t sync to my iPhone (iOS 6x). Get Info on the track in iTunes, add the missing metadata and sync again. Strange but true.
If you already have an Artist listed and think this doesn’t apply to you but still can’t sync up the ringtone, try deleting and then reentering the Artist info and then sync up again. Stranger but equally true.
Other common faults are that the tone is longer than 40 seconds or that you haven’t enabled the iPhone to synch all or this specific ringtone under the Tones tab against the device in iTunes.
Answers the question: Why won’t my ringtones or Tones sync with my iPhone?
Addresses the problem: iPhone ringtones or Tones will not sync from iTunes