Once you have installed your Beta app from App Centre on your Apple device, the first time you launch the app you may get a notification.
This message is normal and just part of Apple's security when an app is installed from anywhere except the Apple app store.
To make you app allow your beta app to run on your Apple device
Select Device Management
Tap on "Plattar Pty Ltd"
Tap 'Trust Plattar Pty Ltd'
Exit Settings and open your app
Accept camera permissions
Make sure you are connected to the internet