to check the powerpath license start - > all programs- > emc-> powerpath licensing tool  You can check the same from cmd using powermt check_registration  Also, please verify for the dead path \ device. powermt display ports and powermt display dev=all will help to cehck these 
I have created and masked dev to a server.  In the server i went to disk management and rescan disks. Powerpath is loading devices from long time. I hope powerpath is crashed.
Powerpath crashed