Windows activation fails when trying to activate Server 2012 R2 on a Virtual Machine

I was struggling the other day with activating Windows Server 2012 R2.  It kept saying the key was invalid, I know it was correct.  I ended up calling Microsoft and this is what they had me do.

If you are having difficulty activating Windows Server 2012 R2 running on a Virtual Machine, you can trigger a manual activation by doing the following:

Launch Command Prompt with Admin rights.

Run the command slui 4

This will launch the phone activation service.

Little did I know after I activated it successfully, it would not join the domain…  After doing some more digging, it appears I set up the virtual switch in Hyper-V to point at one of the four Network Interface Cards (NICs) that was not connected.  Man, I felt dumb after that!