Check on the client has it updated the policy
check this registry entry to know if Application and Device control is enabled..
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SysPlant and the vlaue of Start should be 1.
On the client itself go to View Logs--Client Management-System Logs..and check when was the policy applied..reboot the client once to make sure the policy is applied and working.