I didnt know that.
One of the local players also has the same problem. He claimed 2 items in Twitch and also linked his account in Twitch (Twitch said gog.com connected) but he does not get the Avatar. He also shows his avatar list screen and there is no Kerack Marine there.
I suspect the gog twitch drop has been an issue since yesterday. I try to link my account and it always said "something wrong" >> Twitch Drops - GWENT: The Witcher Card Game (playgwent.com) . Is this might be the case?
I tried this procedure few times always with the ending: