gametime error

[InfinityWol2d]

i have not been play bf4 before . i want to play trial if i fun with it , i will buy . but after i downloaded a game. i try start and i got this message "We could not activate Battlefield 4 (Origin Game Time) on this computer using the Origin Account you provided. Please locate your product key to activate the game using your Origin Account."  how i can solve this or only buy it .