I'm having the same issue as well. Haven't tested it on any other missions, but ATC isn't responding nor are my flight members. I can still hear the recorded unique mission audio though.
On a side note, Ranger, as somebody new to DCS, this was my first campaign purchased, and it has me looking forward to what's coming up in the next mission each time. Very well done, and I look forward to your next campaign.
Thanks again for your hard work!