Problem with incoming voice

I am having trouble with my Asterisk server. I can make calls, however I am unable to hear the other side. I cannot even hear the phone ringing when I call the other person. However, the other person can hear me just fine.

If I receive a call, then I both parties can hear each other fine. The problem is only with outbound calls.

Any clue on how I can fix this issue of having outbound calls working wherein I can hear the other party?