I have got a similar problem. I completed my migration process, and even received a confirmation e-mail from Papaya Play. I downloaded the whole game client again. When I put in my username, and password, the screen remains the same, and I can not log into the game. If I put in the wrong password, I get a message on screen saying "Invalid password or error during connecting to the server."
I even submitted a ticket to highlight the issue to concerned authority. I had attached image of the migration confirmation email that I received from PapayaPlay. But unfortunately, I have not received any response yet.
Comments
Your usernames can be different here at PapayaPlay if you didn't register with same name as Nexon.
Mike