Unable to block Seagate USB device >2T?
We checked GUID of Seagate USB Device is same as Fixed Disk Drivers in EPO
Can you provide screenshot of device manager with the device connected ?
Additionally, try switching the filter(Lower\Upper) on the Policy applied to the machine.
Try this only on a single machine, do not attempt any changes on the main policy.
I tested with 2 different versions of DLP Endpoint（11.400 and 11.500). Blocked U Disk but couldn't block USB mobile hard disk.
Could you test it in your environment?