network error while attempting to run command 'isMaster' on host mongo.example.com

I have enabled `SSL` on my `mongoDB` server. I have set `preferred` as I don't want to make SSL a requirement yet. I can connect to mongo shell easily by typing `mongo` in shell. The problem is that when I use `mongo --ssl --host mongo.example.com` command it gives the following error:

2018-06-02T08:38:02.551+0000 E QUERY [thread1] Error: network error while attempting to run command 'isMaster' on host 'mongo.example.com:27017' :

connect@src/mongo/shell/mongo.js:251:13

@(connect):1:6

exception: connect failed