I was flying just now on ES between CYYC and CYMM.
Faced this problem with tuning to ATC at CYMM (Both were active on liveflight)
I could not tune to ATC from the cockpit as the frequency was not active
Then I got an on guard from Tower:
The ATC was not active from cockpit so I checked in the map view if I could tune to ATC and only Ground active
I use iPad
Have been having disconnect issues for the last few days
Have rebooted iPad, cleared cache and rebooted router too