I am getting the error below while running the PowerShell script.
The export is successful and the user is part of 'Topology Manager Administrators' windows group
Topology Instance and CD are both in the same server.
Also if I run like the below screenshot, the import is successful but when I hit the URL - http://localhost:81/ttm201501/$metadata#mappings I don't see any updated mapping data for cdEnvironment, Website, Webapplication etc.
UpdateExistingItems
parameter is a so-called flag parameter which you either specify (without value) or not.