Here is a procedure to follow that can fix many dysfunctions occurring on iPhone models
Go to the Apple Support site to find solutions to your problem, click on this link: https://support.apple.com
Simultaneously click on the "Home" button (button at the bottom of the screen) and "Power" button (top right) for 5 seconds. Your phone will turn off and on again.
If the problems persist, then perform a "hard reset", click here:
- 1 . Connect your phone to your computer
- 2 . Once your device is detected, click "restore"
- 3 . If the problem persists, you must switch your phone to recovery mode (otherwise known as DFU mode)
Click on this link to find out how to proceed: https://support.apple.com