This is probably a function of the radio (or other equipment) more than the headset. I use the intercom built into my XCOM 760 radio and had to turn the side tone down a bit when I went to the Halo, but realized it had been too loud with my previous headset, also. There should be an adjustment for this in your equipment, or possibly it is muted. If you hear incoming transmissions, you should be able to hear side tone on any headset, IMHO. Check your intercom/radio/audio panel manuals. You might check with other headsets to see if they receive ST. If they do, I don't know what it could be.
Bob Kelly