Detection on sensitive data that is being uploaded to a cloud sync application such as Dropbox, or OneDrive, or iCloud is required for Mac Endpoints.
This is related to MAC OS and Cloud Sync Application Monitoring.
Cloud Sync Application Monitoring support for Mac Endpoints are not supported in the following DLP versions:
DLP Endpoint Prevent 14.x
DLP Endpoint Prevent 15.0.x.
Create two Agent Configurations, one for Mac Endpoints and one for Windows Endpoints.
For the Mac Endpoing configuration, disable Cloud Application monitoring to prevent duplicate incidents from being generated.