As a first step, a forced-restart of your iPad may resolve an isolated problem:
- On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
- On an iPad with Face ID: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.
If this fails to clear the problem, you would be best advised to directly contact Apple Support for assistance - and remote diagnostics of your display.
The link to Contact Support is at top right of this page. During this unprecedented times, using the link is the most expedient route to contacting the Support team.