WebRTC preview not working

While using html publish examples for publishing stream to Wowza Streaming Engine, got an error.

webrtc.js:171 WebSocket connection to ‘wss://5b967f7bee6c0.streamlock.net/webrtc-session.json’ failed: Error in connection establishment: net::ERR_CONNECTION_TIMED_OUTwsConnect @ webrtc.js:171 webrtc.js:260 wsConnection.onerror: {“isTrusted”:true} webrtc.js:314 stopPublisher webrtc.js:255 wsConnection.onclose