Asterisk Feature Codes not working


i installed trixboxv2.2 and made few extensions! i can make calls between the different extensions using X-lite! BUT when i dial one of the feature codes like *65 or *98 i get silence! i also get silence when call is sent to the voicemail although i have all the modules installed! i can see on X-lite that a call is established but i only hear silence, i analyzed the traffic using Wireshark and it shows that there is only one RTP packet being sent from the server to my machine!

please can anyone advice me what to do!

Thank you!