Using IIS 10.* how do I enable WSS support?

I’m getting the following error: WebSocket connection to 'wss://domain.com/ws' failed.

I’ve gone through: https://learn.microsoft.com/en-us/iis/configuration/system.webserver/websocket

and ensured everything is setup the way it should be.

Having a liberty of running my solution by both Kestrel and IIS I can confirm that it’s IIS what messes things up. I can also confirm that it’s not a firewall related one as running it by Kestrel works just fine.

We’re are using .NET Core 8 ASP.NET stack with letsencrypt cert for HTTPs, AllowedOrigins are configured as described: https://learn.microsoft.com/en-us/aspnet/core/fundamentals/websockets?view=aspnetcore-8.0