"LOAD NO" indicates there has been an electrical malfunction. Reset the Controller. See A2000 Service Procedure 15. If the "LOAD NO" still shows, you will need to purchase a new controller (part #A09).
There was a power surge. In order to eliminate a "LOAD NO" situation, plug the instrument into a surge protector.
There is microwave interference. Do not place the Instrument near a microwave oven.