I have a vertical line down the right side of my iPad screen

Take a screenshot - and compare the screenshot with what you actually see the screen of your iPad. Rotating the screen to a different orientation may be helpful when making this comparison.

If the line is present on the screenshot, this implies that the iPad is generating and displaying the line. However, if the line is not present in the screenshot, this generally indicates a screen hardware fault that requires repair.

Take a screenshot on your iPad – Apple Support

Having now confirmed that the iPad has a screen fault, you’ll need to seek repair.

If your iPad is within warranty, you need to seek assistance directly from your retailer. If outside its warranty, but still a device “supported” by Apple, you may be able to obtain out-of-warranty service from Apple. Apple do not offer repairs per-se, but for qualifying devices, you might be offered an exchange for a reconditioned device of the same model and specification; the exchange cost is typically c.60% of the “as new” cost of the iPad.

Apple Support can be reached via the Contact Support link at top-right of this page. Alternatively, you can initiate a case using the excellent Apple Support App:

https://apps.apple.com/gb/app/apple-support/id1130498044

A further alternative is to visit the Genius Bar at your local Apple Store - where the technicians will be able to inspect your iPad and offer appropriate help and advice.

I hope this information and guidance proves to be helpful in resolving your difficulties.