I'm using the GoToMeeting desktop app and I can't seem to unmute all mobile participants. A LogMeIn support agent spent about an hour troubleshooting the issue. She was able to verify that the issue may be limited to mobile users. Basically, when a user joins a room with either iOS or Android app, a room organizer can't unmute that individual. It didn't seem to happen for participants who join with their desktop or laptop.
My GoToMeeting desktop app is running the latest version.