.net core websockets controller endpoint not executing

I've created a .net core controller which, when using postman, I can hit the Get method successfully (validated with breakpoints on the controller constructor and get method) with the URL (https://localhost:44447/api/callsynchronisation/ws)

The code looks like this:

public class CallSynchronisationController : ApiControllerBase
{
    private IWebSocketHandler handler;
    public CallSynchronisationController(IWebSocketHandler handler)
    {
        this.handler = handler;
    }


    [HttpGet("ws")]
    public async Task Get()
    {
        if (HttpContext.WebSockets.IsWebSocketRequest)
        {
            using var webSocket = await HttpContext.WebSockets.AcceptWebSocketAsync();
            await handler.Handle(Guid.NewGuid(), webSocket);
        }
        else
        {
            HttpContext.Response.StatusCode = StatusCodes.Status400BadRequest;
        }
    }
}

In my startup.cs I've added app.UseWebSockets(). This code does execute as expected.

I've set up websockets in angular with the adress wss://localhost:44447/api/callsynchronisation/ws.

When I try to send a message the connection is still in the connecting state

In chrome the initiating ws request never gets a response from the server. I see is the request with a header "upgrade" with the value websocket as expected.

The constructor for the controller does not execute (although it does for the previously mentioned https get request).

What am I doing wrong??