Hi Ike,

Unfortunately, switching to version 5.1.8 and enabling client-side DEBUG logging did not change the situation and did not help us understand the reason for the 404 error on the WS upgrade request.
At this point, as my colleague Dario mentioned, it is interesting to understand how the 101 request reaches the Lightstreamer server and whether it does. Can you confirm that you have access to server-side logs?