Start with the remote battery and whether the gate responds to a wall button or keypad. If it does, the gate is fine and the issue is the radio side. A power surge can upset the receiver or clear its memory, so remotes may need to be stored again. If nothing works at all, check the mains supply and the fuse at the control board.
Our technicians test the receiver, the antenna and the stored remotes, and can add spare remotes at the same visit.