It's saying that you need to verify yourself to charge NX.
If you were able to charge NX fine before, I'd reckon it has to do something with them changing something recently, as I've seen this incident happen in one other person's account over in the chat.
Have you got any credentials or so you can use to verify your acc?
I created this and my alt acc when just the email was necessary to verify a nexon account, bakc in 2009~2010.
And no, I never get NX before.
A couple of months ago, they ask me to confirm the email again with a "confirm like" message everytime I logged in, and so I did.
I need to confirm with a phone or something?