Download and run the Advanced Recovery Companion for Windows when you need help restoring and recovering supported devices. Try restarting or resetting your device before using this tool.

If restarting or resetting doesn't work, back up your stuff. Then, use this tool to download and install an approved version of Windows. The installation process will delete everything on your device (including your apps, content, and media), so it’s important to have a backup to restore everything from.