No audio on outgoing call using Bria (Windows) and Fritzbox

I have a Fritzbox 7270 and wish to use a Bria (Windows) soft phone with it. I have created a WAN/LAN phone on the Fritzbox on extension 620 and create a VoIP account on Bria that has registered fine. When a call is received at extension 620 everything works fine (audio in both directions). When it is initiated at 620 there is no audio.

Please help