Unable to connect to SignalR (Not Azure SignalR) after deployment to Azure App Service

ngOnInit(): void {
    var hubConnection = new HubConnectionBuilder()
      .withUrl("https://domain..../v1/instruments/instrumentHub", {
        headers: {
          "Ocp-Apim-Subscription-Key": "Dummy Data"
        },
        withCredentials: false,
        transport: HttpTransportType.ServerSentEvents,
      .configureLogging(LogLevel.Trace)
      .build();

    hubConnection.start().then(() => {
      console.log(1)
    }).catch((e) => {
      console.log('error', e)
    })
  }

{ "statusCode": 404, "message": "Resource not found" }

        withCredentials: false,
        skipNegotiation: true,
        transport: HttpTransportType.WebSockets,

[2024-04-01T05:07:51.737Z] Debug: HubConnection failed to start successfully because of error 'Error: WebSocket failed to connect. The connection could not be found on the server, either the endpoint may not be a SignalR endpoint, the connection ID is not present on the server, or there is a proxy blocking WebSockets. If you have multiple servers check that sticky sessions are enabled.'.