Normally, you would not get this message immediately after power-up. It usually only comes after something in the electromechanical system gets too hot.
However, you will get this message if there is a problem with the pedal cable. Check the pedal cable connection. You will get this message if the cable is not properly connected. Was the piano moved and then it had this problem? It is possible that the pedal cable is simply not connected or there is/are bent pin(s) in the connector.