I am working on a model for a project where multi-zone air handling systems are being converted to single-duct VAV systems. I have already completed the system changes so that all of the air handling units are single-duct VAV. However, I am unable to change the zones to include VAV boxes. Under each zone in the "Air Flow" tab, the "Zone Terminal and Fans" section is all grayed out and will not allow any changes. I tried deleting the zone and re-creating it, but I still have the same issue. Any advice is much appreciated!

Rob