When I open an AECOsim model and select the Place Rectangular Duct( or round duct) I receive the following error:
First try a "Repair", from Control Panel > Programs > Programs and Features, right-click on AECOSim Building Designer and select "Repair". If after the repair is complete the issue still persists then uninstalling and reinstalling AECOsim Building Designer normally resolves the issue.