I got the same problem here. Me and a fellow ArmA player tried the last version of AGM (he just updated it, I personnally installed it for the first time) and we couldn't hear anything from some weapon fire.
We did tests with different weapons. Sometimes we both heared sounds. Sometimes none of us could. Sometimes one of us just heard fire, the other one did not.
Any idea ?
We did the test with both Vanilla Weapons and moded Weapons.
EDIT :
We are also using Teamspeak with the last version of Task Force Radio.
EDIT 2 : OK problem found, the volume of the radio needs to be at its highest level in the audio options from the game.