I am new to mongo. Recently created an account in mongoLab.
I am trying to connect to the database using the below statement.
mongo ds039487.mongolab.co
Thanks to pneumee.
The issue was because I was using my mongolab.com username and password, instead of the database username and password.
It is working now.
Old thread, but just in case it helps anyone else: my problem was using shell version 2.4.9 to connect to mongo db version 3.0.7 (http://docs.mongolab.com/connecting/#mongo_shell).
Updating my shell sorted it (https://docs.mongodb.org/master/tutorial/install-mongodb-on-ubuntu/).
default users in db
login: admin
password: admin
check users in https://mongolab.com/databases/MYDBNAME#users
my problem was being putting login and password mongolab
OK - I figured it out and would also like to add onto pneumee's answer.