Hi @Jon_C I can reproduce that error if I put in the host name of my server on the Hostname tab. My MongoDB instance is bound to only the localhost address bindIp: 127.0.0.1. Due to this I need to use a host name of localhost on the Hostname tab.
In the More Options tab you will provide the actual machine that you would ssh into.
Hopefully this takes care of your issue. If not please provide screen shots of the two tabs and your /etc/mongod.conf file as that might help to troubleshoot.