Franz In my case, Pusher recognizes the connections but doesn't sent any message.
Sometimes in console it would show WebSocket connection to 'ws://ws-mt1.pusher.com/app/2f6bb1e80d0399f2e8b2?protocol=7&client=js&version=3.0.0&flash=false' failed: WebSocket is closed before the connection is established
.. but most of the times it doesn't.
I am not using Cloudflare, but I am running php7. Could that be the reason?