Choosing the rear (back) camera on iOS worked in testing 1 week ago but did not work during pre-show test today.

When connecting via advanced.vmixcall.com the iOS user has the camera select menu present, but selecting the rear facing camera does not switch the camera. The front facing camera stills sends image through, never changes.
This behavior was repeatable on both iPad and iPhone running iOS 15.3.1
Behavior was also repeatable on beta.vmixcall.com
edit to add: rebooting the device did not change this behavior.

When connecting to vmixcall.com (non-advanced) the iPhone shows the option to select the rear camera and can successfully connect, showing the rear camera.
Repeating this on the iPad: the option to select the rear camera was not present; could only connect with front facing camera.

The only thing that changed between testing last week and testing today was location: moved from a home network to a corporate/venue network.

Any troubleshooting steps or advanced settings to try appreciated.

I should have stated in the original post that we did power cycle the iPad. The issue was not resolved (behavior was the same) after reboot.