I got the same issue.I tried PayPal - no luck. Tried credit card (which works perfectly fine on any website/game) but no avail either. I keep getting the "Unfortunately an error has occured. Please try again later!" Message that pops up in a split second and then disappears again.Due to this issue, I haven't purchased gems in over a year while I used to spend €30 every 1-2 months.Recently tried to purchase an expansion for my second account. Same result through guildwars2.com website as well as in game...It's frustrating. I want to spend my money on a game I love, and they don't want it :<