The Avegant video headset is not really compatible with the Mavic drone. The only way it sort of works with the Mavic is in WiFi mode plugged directly into the phone/tablet. It has to be on wifi mode or in RF mode with an HDMI-capable tablet -- not just a phone or tablet with MHL/Slimport out -- the tablet must have an ADDITIONAL HDMI-out option. Otherwise, the Avegant video headset won't work with the Mavic.
Keep in mind that in wifi mode the range is highly limited.