Adventurers,
If you are receiving error messages when you attempt to purchase NCoin, there are a few other payment options you can try. You may want to refer to this link for more details:
http://www.lineage2.com/en/marketplace/buy-ncoin/
Use a Credit Card.
Use Paypal.
Use BillToMobile (Not available for Prestige Pack purchases).
Purchase NCoin Cards from your local GameStop (http://www.gamestop.com/dlc/ncsoft-ncoin-25/110280).
Purchase NCoin Cards from Amazon.com (http://www.amazon.com/LINEAGE-NCOIN-5500-Online-Game/dp/B00D6RZ5IQ/ref=pd_sim_vg_1?ie=UTF8&refRID=18B152QHE4VN719A4H88).
If none of these options work, please click here (https://support.lineage2.com/hc/en-us/requests/new) to contact Support.