I found an easy solution and explanation. First, remember that iTunes treats your ringtones very similarly to your music. In order to load it to a device, it must reside on your computer. I always place my ringtones in my subfolder of my downloads. Otherwise they can get deleted easily if they only reside in temp folders.
In iTunes, click on the Ringtones section of your iTunes library. If you notice a yellow ’!’ tag left of the ringtone, simply click on the ringtone with the tag and you will see the error message. It most likely will indicate that the ringtone file cannot be found.
I find the easiest way to correct this is to simply delete the ringtone in the iTunes ringtone list. Next, save your ringtone in a folder in your computer library that will not get deleted and will backup with your normal backup routine. Next move the ringtone to your iTune Library. After Syncing your device, all should be good to go and you will have a better understanding of your iTunes data management.
Good Luck!
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