Check your CAN voltage. Should read about 2.4vdc from CAN low to G24 and slightly higher on CAN high. If voltage is funky, unplug the riser and read the board pins. If the voltage is better there is probably a bad HN card. If voltage is funky on the board, it’s probably that CPUA. Do make sure you matched the header jumpers. Power off should have 60 ohms from CAN high to CAN low.
