Unable to Buy NX?

Pandere

Payment Method Unavailable

This payment method is currently not available. You will be able to charge again on 04/26/2021.
We apologize for the inconvenience and appreciate your patience. (Code:50422)

Do i just wait for 2 weeks or?

Neospector

You reached a charge limit on that payment method, likely set to prevent chargeback fraud or to prevent people from maxing out their credit cards in a single go.

https://steamcommunity.com/app/212200/discussions/0/154644349173049799/
http://forums.vindictus.nexon.net/discussion/5094/cant-buy-nx-code-50422

You could try a more indirect method, such as buying through PC Game Supply or Offgamers, or wait until the 26th to continue with that payment method.