Answer to "Why will my Bluetooth setting not turn on (stuck on spinning gear)?"I found, quite by accident, that when my daughter's 5C had this issue, sliding a fingernail between the screen and the polycarbonate casing at the midpoint of the right side of the phone fixed it instantly. It would stay fixed for quite some time and then pop up again sporadically, and this fix worked each time. Obviously this is only applicable to the 5C due to the flexibility of the polycarbonate case (no way you're getting a fingernail in a 5 or 5S like that), but if you've got a 5C with this issue then it's worth a try. Like you, I first tried all the solutions I could find online, to no avail. I believe Minho's answer is indeed on the money. It's just that in my particular instance this random fix worked.