I've been an appliance tech for 20 years.
Not sure I followed this correctly, but you say the fridge is working fine, except the display is blank?
I would guess then that there is fine voltage to the board, and it IS on but no output to the display.
No display but working fine, yes 95% chance it is the board. Reset your connections to the board and power it up again. Test the board itself? Not likely. Most places will return it if that isn't the problem, but you will have to pay a restocking and testing fee. Have had little to no luck with local places anywhere testing equipment for function. They don't have the full hookup needed to do it right.
