Perform a power cycle or factory reset of the device.
INSTRUCTIONS & INFO
There are multiple ways to reset your device if you are experiencing issues. The first step is to power cycle your device. Press and hold the Power/Home button, then select Power off.
To turn the device back on, press and hold the Power/Home button until the screen lights up.
If a power cycle doesn't resolve the issue, you can perform a factory reset. A Factory data reset will revert the device back to factory settings. It will permanently erase all personal data, preferences, settings and content such as pictures, ringtones and apps that are saved to the device. It is recommended that you save (backup) important data before proceeding. To perform a Factory data reset, from the clock screen press the Power/Home button.