When I switch off BLE on my Fenix 3 and later switch it on, it will not connect to GCM anymore, until the pairing procedure is done again. The problem first occurred after updating GCM from 3.18 to 3.19. I have given GCM all the permissions that are available in Android 6. It does not make a difference whether the phone has an internet connection or not. The phone is a Fairphone 2 with Android 6.0.1.
I'd appreciate it if anyone who is experiencing the same issue would mention it (if it is only me I'm not going to bother Garmin Support).
Edit: It is probably common.. there's an app to remedy it.. Reconnect to Garmin (GCM runner).