Maybe this will help? With the Ospi powered up and expander connected, no zones active: COM to Zones 1-8 indicate ~7.5 VAC, Zones 9+ indicate ~11.5 VAC. Zone 1 active = 26 VAC, Zone 9 Active=~11.5 VAC (i.e., no change).
What values should I see on the expander out pins?