Today, I tried to trade in one of my older iPad Minis to GameStop. They refused, claiming it is "locked". I have no idea what this means. I was not present when this happened. I've never used a passcode, and before taking it in, I factory reset it, so it should not be locked in any way. Any idea what's going on?
iPad
If the iPad is truly factory reset and at at the Hello screen then GameStop told you wrong. It is either locked or not. If not, they are wrong. If yes, you have to unlock it. These are your only options other than calling Apple ID support.
If you forgot the Passcode:
https://support.apple.com/en-us/HT204306
If you forgot the Apple ID Password:
https://support.apple.com/en-us/HT201487
If you forgot your security questions:
This usually means that Find my iPad is turned on. Try Settings > iCloud > and turning it off.
Where and how?
On your iPad go to the Settings App > iCloud > scroll up and look for Find my iPad > turn it off but you will need your Apple ID password.
That doesn't make sense. The iPad is factory reset. I would have to enter all the info again to access the settings, after which I'd need to reset it again.
iPad Mini locked?
