To connect to a customer's system, by default COM uses the settings of the COMAdmin service user and COM Admin rights group configured in the system's security settings.
Those settings are present by default on new systems and just need the service user account enabled and service user password set. That is normally done automatically during the initial connection of a subscription to COM.
However, on existing older systems being converted to subscription usage, the service user and rights group may not exist. In that case, they need to be created and configured manually.