After a new Cloud Detector, for the Cloud Detection Service, has been enrolled in DLP v15.
The CDS has also been registered successfully in the CloudSOC (CASB) console.
However, there are no incidents or detections occurring via the related technology (WSS or CloudSOC).
Firstly, be sure there are no two-tier indexing issues, as per this related article : be sure all indexes are present, and the CDS has a full profile and policy matrix.
Secondly, in contrast to settings in DLP v14.6.x, in DLP v15 and above it is required that a "New Configuration" be setup in order for successful detection via Cloud Services.
For all versions of DLP Enforce, with Cloud Detection Service, and any of the following associated technologies:
For versions 15.0 and 15.1,
Follow the steps given in the Admin Guide (also available online, via the Symantec Help Center, by clicking on the "?" in the Enforce Console), in the section entitled "Managing Application Detection":
After you have deployed and configured your Symantec Data Loss Prevention Cloud Service Connector, you can configure cloud application detection on the Manage > Application Detection > Configuration page
Take note, however, that while the documentation suggests you "can" perform this step, it is in fact required.