Hello,
Your getting the access denied message when the Exchange powershell url isn’t local.
External virtual powershell permissions are alot more complex to apply then the local one (i personally never got that to work).
So the most easy way is: install SolidCP Server on the exchange 2016 CAS –> in the SolidCP Portal change the connection settings of the existing exchange 2013 server –> since you already flipped over the provider ID you should be more or less set.
Regards,
Marco