Diagnosis
The thermostat is not detecting line voltage. This is almost always an installation wiring error, specifically reversed Line and Load wires.
How to Fix It
Power off the circuit breaker. Remove the thermostat faceplate. Confirm wire connections. The black wire from the wall must connect to the Mysa's L (Line) terminal. The red wire from the wall must connect to the Mysa's 1 (Load) terminal. The white neutral wire must be secure. Reattach faceplate and restore power.
If That Didn't Work
Verify the circuit breaker is fully on. Use a multimeter to confirm 240V AC between the black and red wires at the wall with the breaker on and wires disconnected from the Mysa.
Heads Up
Incorrect wiring can damage the thermostat. Always confirm power is off at the breaker before handling wires.