Authorization required in Lobby

I'm a linux user, sò I know the S.O. isn't supported, but I try to ask you my problem.

In lobby, when i go to buy a item appear a box that ask me the authorization. You can see the box in ~~ the attachment~~ LINK.
I try to write my credential but I don't have success.

I'm wating your responce, Best regards, Raks88