If you encounter the error: "Unable to Open Catalog: The catalog couldn't be opened due to a locking conflict. Please check permissions on the catalog folder", find the catalog package in Finder. Right-click on the catalog package and choose Get Info:
In the Get Info window, uncheck the Locked property.
The catalog should now open properly.
Navigate to your catalog folder in the Explorer. Check the Properties of the catalog package by pressing right-click -> Properties -> Read-only (make sure there is no checkmark next to this option).