It's entirely possible that I'm doing something wrong here, but nevertheless.
This happens in created fast missions, or missions I throw together in the ME.
I'm in the Hornet, easy communications are ON, the airport is set to BLUE, but all the ATC options are dark grey, i.e. unavailable as if they are not in range, and don't respond to any calls. Both when I'm on the ground at the airport, and in the air.
AWACS - works.
Flight - works.
Ground crew - works.
JTAC - works.
The radio also selects the correct channels (easy comms), it's just as if ATC (and ONLY ATC) is on strike...