Luxaire Model-PBKM-LD 14 N 100F. Furnace quit working. After troubleshooting, determined circuit board had issue. Replaced circuit board, now getting reversed polarity/bad ground code. Wiring checked by serv. Tech determined all fine. Any Ideas??

Make sure the ground is good all the way back to the electric panel.

Reverse the 24 volt wires from transformer to board.