Did you manage to solve this? I get the same error when trying to create an ArcGIS site with 10.6.1 on a Windows Server 2012. I change the firewall to accept the following programs:
- <ArcGIS Server installation location>\bin\ArcSOC.exe
- <ArcGIS Server installation location>\framework\etc\service\bin\ArcGISServer.exe
- <ArcGIS Server installation location>\framework\runtime\jre\bin\javaw.exe
- <ArcGIS Server installation location>\framework\runtime\jre\bin\rmid.exe
Also added ports in the firewall: 1098, 4000-4004, 6006, 6080, 6099, and 6443.
Added arcgis user to the Administrator group.
I previously installed ArcGIS server 10.6 on a Windows Server 2012 and could create a site without any problem.
About above suggestions, to test connection to the REST service. Why testing that when the site isn't created yet? This problem is not about connection to the REST service. It's about creating an initial ArcGIS site and where it fails for us.