@th3j35t3r it seems the mobile interface can be problematic if the screen doesn't auto-rotate. In Portrait mode you can't see the drop down for acknowledging the permission issues that seem to pop up by default. Once I ack'd the errors it put me in the conference and I could activate the mic/cam.
@th3j35t3r Further for users in portrait mode the toggle button for the gallery view over/underlies the Hang Up... so use caution if you're locked into portrait.