The transmitter is not programmed on the operator or is programmed to the wrong radio channel.
The transmitter battery is flat or there is no mains power supply.
The fuse or the main switch is not switched on.
Have a specialist check the voltage supply at the operator.
The emergency release was activated; unlock the sliding gate operator.
The safety device has been activated, e.g.: safety contact strip, photocell, emergency stop etc.
Holiday mode was activated at the Wallstation; the command devices are locked.