Unable to trigger external DLP incidents with DIM (Data In Motion) Gatelets.
External DLP incidents for DAR (Data At Rest) Securlets can trigger.
CASB access enforcement policy's can trigger.
Verify the DLP Scan filter is setup correctly and synchronized.
Verify the scan filter's Device Management is set to ANY and not managed.
Currently a machine with the WSSAgent does not constitute a managed device. Symantec will be addressing this in a future release.