problem with display

Also, I suggest contacting/reaching out to Apple Product support and services.

Tap on the first link below and scroll down some to get to the Apple Product Support section and phone numbers for your location/region.

https://www.apple.com/contact/

OR

https://support.apple.com/en-us/HT201232

Best of Luck to You!

I have not experienced that, but what troubleshooting have you tried? Has the iPad been dropped? Try creating a screenshot with the iPad and look at it. If the line does not appear in the photo, and just remember when you are looking at it where the actual defect in the screen is, then it would indicate a screen hardware error. You would need to contact Apple Support. Use the Contact Support link at the top of the page to contact them to see about service options.