TeamViewer 11 Free licence - Meeting Video call - remote contact always muted

[johnsonb52@comcast.net]

With TeamViewer 11, Free licence, Win 7 32-bit - Meeting, Video call - remote contact always muted, Microphone control disabled on remote contact's TeamViewer.  When he tries to un-mute in Audio conferencing, Voice input, TeamViewer resets him to mute within a few seconds.  His microphone works, and briefly shows a Signal.  Video works normally, but remote user can't un-mute his microphone.  We have video, but I can't hear his voice.
1. Can I use Meeting, Video Call with free license?
2. How can remote contact un-mute his microphone on a Video Call?