you might already be doing this but in order to talk on the AM channel you need to press ctrl + 2 and to talk on the FM channel you need to press ctl + 3 and to get back to UHF you need to press ctl + 1. after that you can press your teamspeak button to talk.
Also make sure the radio is on and tuned to the same freq.
The keys are configurable in the TARS control panel so you can match them to HOTAS mic buttons but the radio menus will come up when you do that.
some like it that way some do not.
thanks
76th Falcon