When I installed Sitecore 10, I got this ANCM Out-Of-Process error while trying to connect to the identity server.
This could be reproduced easily when trying to connect to the identity server with this URL:
Looking at the Event Viewer (Windows Log/Application), I could see a much better description of the error
I have installed numerous versions of Sitecore on my computer. Right now I have 9.0.1, 9.3 and 10.0 running simultaneously. What the error says is that I need a specific version of Microsoft.NETCore.App (2.1.16) that was obviously not installed by SIA when I installed Sitecore 10.0.
You can check which versions are installed by opening a Powershell window and type the command
I can verify that I don’t have the runtime for Microsoft.NETCore.App 2.1.16
So I just downloaded the correct file from Microsoft .Net Core 2.1 Download page
After installing it, I can verify that the runtime is installed with Powershell
The page I tested to connect to the identity server is now working