As well as connecting to an admin host you can also add connections directly to a REST API port, this will be beneficial if you are connecting to a cloud server and only the REST API port has been opened.
In the settings.yml replace the  for the connections parameter with:
- url: https://<server name portnumber>:<HttpPortNumber of TM1 instance>
- name: name to be displayed on Arc.
Arc uses the TM1 REST API to connect to the TM1 instance, the TM1 REST API is not enabled by default. The instructions how to enable it can be found here: