I believe it is the button labeled "Push Button" in the picture below. The complete service manual is available at the link below as well!
Service Manual <----- CLICK HERE FOR THE SERVICE MANUAL
You must push that button with the power on to the machine. That is how it is reset. Is that what you mean? The button you need to press is labeled "Alarm Reset" on the board.
The temperature of the suction line in the refrigeration circuit is limited by the high temperature safety. This protects the unit from excessively high temperatures. If the evaporator temperature rises above 127°F ± 7°F (53°C ± 4°C), the thermistor operates the safety. This shuts down the circuit and the icemaker automatically stops. The control board will signal this problem using 1 beep every 3 seconds. The alarm reset button on the control board must be pressed with power on to reset the safety.