HelpInvaild Cd Key

i have a key which should work fine but its say invaild i have steam
i dont know why the key dont work its not buyed someone send him for free to me he say by him works fine

What.

wut? /tooshort

What did you call me?

If you change the key and open it with steam steam will automatically re-write the key to the old key you had so you need to open with play with 6 or DayZ commander

yea.. i thin he ment " i got a key that someone sent me but it invalid, the person send me it say it was legit"