I was playing the game last night and early morning and got off around 3:00 am-4:00 am EST.
However, I attempted to play today but I was prompted with inputting a 16 digit product key to play Maplestory now...this game has always been free and never required a product code. I have been playing since the Beta and my account has never run into issues(even though half my characters are banned for "hack" reason and they haven't leveled or been played since I stopped playing years ago, but thats another issue) So I am wondering what is happening as I don't have any answers and I can't find any answers on the website.