I had been running the production app on my iPad then it suddenly stopped working. I ran into the same problem a blank screen and no cameras.
I tried every method known like restarting device, force app close, uninstalling/reinstalling nothing worked. I still got a blank app with no cameras or any of my products showing up.
Then I found a solution that worked for me. I installed the Beta app and poof…everything started working normal again. Obviously the production app has got a major bug on iOS.
(Step 1) You can download TestFlight for iPad/iPhone then click on the link (step 2) and download Beta.