Hello @badams,
If you are using the chan_sip, then add these settings to the sip settings module:
prematuremedia=no
progressinband=yes
If this is still does not work for you, you will need to add the Progress application to your dialplan.
If you want to allow video calls between the GXVs, make sure that you add the h.264 codec list and that you are allowing video calls.
Thank you,
Daniel Friedman
Trixton LTD.