Your radio isn't affiliated with the system and until it does, you'll get the No Comms error.
In a little more detail: Your radio is receiving the system control channel and it's data stream, but for whatever reason, the radio cannot communicate back to the system.
This may be one of many things such as:
The radio is just on the fringe of the system and doesn't have enough power to reach the tower.
The radio is getting a reflected signal that is strong enough to keep integrity, however the radio cannot follow that same signal path.
The tower is being overloaded (not likely)
The radio is off spec or has the wrong antenna which makes it's SWR off (possible)
Transmitter is damaged
There is interference on the TX frequency.
The system is TDMA and you are out of phase (the speed of light is finite and your signal takes too long to travel and overlaps the next time slot)