Error 200 account authentication failure

[I1sL0l1]

I recently downloaded the new launcher ''NC 2'' and when I try to start the game it says ''Failed to connect to server. SystemErr- (200: Account Authentication Failure). I'm in EU and my friend is also in EU but he can connect without a problem. I looked for solutions to this problem and I found one, but I couldn't really understand it (I'm kinda a dumb person). The solution is the one in the ''account support'' page. As I said I'm kinda dumb and didn't really understand it, and I wanted to see if nay of you have had the same problem, and if you fixed it, could you try and tell my how you did it? Thank you for your time.