Bad request from Blazor using Signalr after deployment on IIS

I have implemented a Blazor application with Signalr which works fine locally, but when I deploy it to a server with IIS it throws:

blazor.server.js:15 [2021-03-11T15:35:28.868Z] Error: System.Net.Http.HttpRequestException: Response status code does not indicate success: 400 (Bad Request).at System.Net.Http.HttpResponseMessage.EnsureSuccessStatusCode()at Microsoft.AspNetCore.Http.Connections.Client.HttpConnection.NegotiateAsync(Uri url, HttpClient httpClient, ILogger logger, CancellationToken cancellationToken)

When I compare what Is happening locally with what is happening on the server it looks like it is this request that fails

[2021-03-11T15:54:20.865Z] Information: WebSocket connected to wss://localhost:44312/_blazor?id=VQLOPgZDJ-bXAb1CqhG1Vw.

I am running IIS version 10. I have not added the WebSocket protocol to my IIS install.