Windows Admin Center Computer Management Specified computer 'computername' is not a Windows PC.

Hi, 

Trying to figure out why Computer Management in Windows Admin Center 1904 doesn't recognize any of my computers

Have tried it with a 2012R2 DC and the very Server 2016 computer Admin Center is running on 

Have tried the following settings:

enable-psremoting
Set-NetFirewallRule -Name WINRM-HTTP-In-TCP
Get-NetFirewallRule -DisplayName "SmeInboundOpenException"
Set-ItemProperty -Path 'HKLM:\System\CurrentControlSet\Control\Terminal Server' -Name "DenyTSConnections" -Value 0

Get the following error on both:

Specified computer 'computername' is not a Windows PC.

Can't seem to find any information pertaining to this error message in any forums or troubleshooting guides.  Can anyone tell me what I can do to remedy the situation?

Thanks!