I bought two times crysis 2 digital version and i have two different serial keys

i am use a key for multiplayer and my friend use another key for play online with me on same ip(modem)

but system says to me "your details name or password is wrong or missing"

but only im enter the play online everyting is good no issue and my friend only enter online with out me and everyting is good

but we dont enter both online

sorry my bad eng