I can not register to game

I can play only demo even tho I bought minecraft on 12th april 2018 16:05:26 bought from g2a the product key is G4M7M-M4G3B-Z9T6Q-D7D6H-W4T4J don't know if its the right one but it should be so if you could do something with it I will be very thankful for any response