I chose the "fast" ring update on the windows insider app in order to get the preview for windows 10 on my lumia 1520. It updated fine but since the migrating data process began, it has been stuck in a continuous reboot loop. The screen shows the nokia logo and the windows logo briefly, then shows the at&t logo (since I bought the phone in the US) with "not for resale" written in the bottom left corner. How can I fix this? I don't mind losing all my data.