webIM掉线，未触发断线监听

掉线前的日志：

--->- event:c_init, data:{"appkey":"19b41caab6b93281e0677c6a","random_str":"fQvc7al9PdJZ65uU2pdi","signature":"4476f19fd7aa4111dca879e8d1e9cfa5","timestamp":1568171409566,"flag":1,"fromPlatForm":"x","rid":1224258188}
---<- event:ack, data:{"rid":1224258188,"event":"c_init"}
---<- event:c_init, data:{"rid":1224258188,"code":0,"event":"c_init","message":"success"}
--->- event:login, data:{"username":"1004","password":"34451aea659b5aa64dd946af3b5104f7","version":"2.6.0","rid":1043837318}
---<- event:ack, data:{"rid":1043837318,"event":"login"}

WebSocket connection to 'wss://ws.im.jiguang.cn/socket.io/?EIO=3&transport=websocket' failed: WebSocket is closed before the connection is established.

请帮忙看一下是什么原因。