Invalid URI when attempting to validate the Network Controller REST URI

[jcorrigan14]

Hello,

I am running into a problem when adding the cluster to Windows Admin Center. I am able to add the cluster name "azstackcluster" which is found.
But then when I try to validate the Network Controller REST URI "https://nc01.contoso.com/" it says "Invalid URI".
I did install the RSAT-NetworkController and have followed all other steps of the documentation both here and from the MS docs.

Here is a screenshot of my error from the Windows Admin Center:

Any guidance would be greatly appreciated, thanks!
-Jack