When using the Ipad with the demos, it seems to be looping with requesting access to the camera. "Refresh the page to enable camera access for AR."
What version of iOS 13 are you running? I assume you are using Safari?
I would check that you haven't disabled camera access at either the app or site level.
Check: Settings -> Safari -> (scroll down to "settings for websites") -> Check that Camera/Microphone are set to either "Ask" or "Allow"
Also, you can check settings for an individual site by clicking the "aA" button at the left of the URL bar, then go into Website Settings and check permissions there as well: