Make sure the valves have the following configuration:
Cooling valve = Normally Closed/Failed Closed (UO12)
Heating valve = Normally Open/Failed Open (UO11)
In the thermostat, set it as Direct Acting.
Direct action means that the controller output rises if the measurement increases. Indirect (reverse) action means that the controller output drops when the measurement rises.
When temperature rises, cooling is required, controller starts to increase output voltage on both UO11 and UO12, the normally closed cooling valve will start to open and the normally open heating valve will start to close.