I ordered 2 circuit boards, Main board (under fridge) and door circuit board. Either one could have been the reason for the communications error. Didn't want to take a chance and order the wrong one and wait a week for a different board.
The problem was the main board. I will keep the door board as a spare. The replacement board was not identical to the original so there were adapter cables that had to be installed. A little tight fitting into the original box but it worked.