Question-and-Answer Resource for the Building Energy Modeling Community
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You don't need an AirLoopHVAC:OutdoorAirSystem at all.
The problem is that your loop is probably autosized, and it's getting sized to a zero flow. That can happen for a variety of reasons.
Check that the zone you serve does have a high cooling load (check the equipment and the schedules attached to it). Check that the zone also has appropriate thermostat setpoint schedules (eg 40F heating / 80F cooling). Also double check the Airloop Sizing:System and the zone Sizing:Zone inputs. And check the SetpointManager you placed on your AirLoopHVAC.
Note that if the only thing you're trying to cool down is a single zone, I'd suggest not using an AirLoopHVAC at all, but one of the ZoneHVAC object that can use a Coil:Cooling:Water (PTAC for example, or 4 pipe FCU)
