iOS App Does Not Activate iPhone Camera to read QR Code

New user and first post.  I've successfully added a Base Station, Keypad and 4 Motion Sensors and when asked to scan the QR code for the Base Station the app activated the camera and successfully read the QR code.  These installed elements test perfectly (though I haven't yet found a way to actually test the siren i.e. test the thing actually emits an ear-splitting sound).  However, when trying to add a camera through the app the camera isn't activated and nothing I do changes this.  I've tried using the iPhone, iPad and rebooted both to no avail.

Any suggestions gratefully received.

***Now Resolved***