After installing a 10.6 Base ArcGIS Enterprise deployment with GeoEvent Server, creating a new stream service and attempting to subscribe at REST results in an incorrect message “You have unsubscribed”.
It is possible that GeoEvent Server missed a notification from ArcGIS Server that the security topology has changed if the issue was encountered after federating the ArcGIS Server associated with the GeoEvent Server with an ArcGIS Enterprise Portal.
The 'Default' server connection registered with GeoEvent Server for a federated ArcGIS Server must be of type 'Portal'. At 10.5.1, notification was added to ArcGIS Server enabling GeoEvent Server to know when federation has occurred and switch its 'Default' server connection from 'Server' to 'Portal'.
The issue was not reproducible in environments in which the base ArcGIS Enterprise was established and ArcGIS Server federated with Portal before installing the GeoEvent Server component.
A workaround identified when it is observed that GeoEvent Server still has its 'Default' server connection registered as a 'Server' type connection is to:
1. Export current GeoEvent Server configuration to an XML.
2. Reset the GeoEvent Server configuration.
3. Enter credentials for the 'Default' registered server connection so that it validates (connection type should be 'Portal' after configuration reset)
4. Import the configured inputs / outputs from the XML.
An alternative work around is to register a 'Server' type connection explicitly with the ArcGIS Server associated with the GeoEvent Server and use this connection ... not the 'Default' connection to publish / re-publish the stream services.