New game to me. Test report - check switch 56 - Bookcase Opto 4. When I check the switches, none of the switch in the row 6 - White-Blue register.
Unplugged the Opto board, and it made no difference. We have checked for continuity and power on both sides of all the switches for that row, all look good.
Replaced I/C s, and still nothing. Any ideas??