Windows Server doesnt come with a functional version of direct X and the one that AMP tries to install either fails or doesnt include what is needed to run Icarus.
After trying to run the server manually from the explorer i got the error:
You need to have Direct X runtime installed.
Tried to download the installer from Windows and it failed to download because Windows Server hates it for some reason.
Downloaded and installed it. Installed an Icarus instance and ran it.
New error codes finally!
I found that you cant run the instance from the a folder in the parent C drive.
You need to set your Datastore to a location with full read/write capabilities.
I had a second SSD in my server labelled S:
Created a new Datastore there, created a new Icarus instance in it, and VOILA!
The server updated fully from SteamCMD and ran successfully.
Searched for my server and connected in the game sucessfully.
Hope this helps. What a massive hassle to get one game server working.
My default recommendation on any Windows install is to install all the C++ redists (32 and 64 bit) and the DirectX runtimes. Saves these sorts of headaches
And, yes, the web installer for the DirectX runtimes never works on windows server