First, set up the remote connection of Mongo server:

vim  /usr/local/mongodb/etc/mongodb.conf

Note out:

bindIp: 127.0.0.1  # Listen to local interface only, comment to listen on all interfaces.

The binding IP is 127.0.0.1 by default. Only local connections are allowed

bind_ip = 0.0.0.0

Restart Mongo remote connection:

service mongod restart

Robo3T reports error connecting to remote MongoDB: Failed to refresh ‘Collections’. Error: ListCollections failed:
Possible version issue.
Robo 3T 1.4 -> MongoDB 4.2
Robo 3T 1.3 -> MongoDB 4.0
Robo 3T 1.1 -> MongoDB 3.4
Robo 3T 0.9 -> MongoDB 3.2
Robo 3T 0.8.x -> MongoDB 2.4.0
Download the corresponding version.
https://github.com/Studio3T/robomongo/releases/tag/v1.3.1