Diagnosis
The wall control has lost power or its connection to the motor unit. The two dashes indicate no communication. Check the wiring.
How to Fix It
First, check the connections at the back of the wall control unit. Ensure the wires are secure under the terminal screws. Next, check the connection at the motor unit. The wires plug into terminals 1 and 2 on the logic board. Ensure they are seated firmly. If connections are good, the wall control itself may have failed.
If That Didn't Work
Try a known-good wall control. If a new unit works, the old one is faulty. If the new one also shows dashes, the problem is in the logic board's terminal circuit, requiring board replacement.
Heads Up
Always disconnect power at the opener before checking or touching wiring connections. The terminals carry low voltage but it's a safety best practice.