I need to reset an iPhone. My grandmother somehow locked her iPhone with a pin and no one knows the code. I have a backup of her phone in my iTunes but I need to reset the phone before I can restore that backup.
When I attempt to restore the phone it tells me it has a problem downloading the software. I've tried on multiple computers. There isn't an iCloud account for this phone so I cannot reset it using that method.
How do I reset the phone so I can restore it and get it working again?
It's an iPhone SE running the latest iOS.