I have been having this problem for days now. The only way I can even sometimes buy gems is 800 at a time on any of my cards. The info was put in correctly each time and I have more than enough funds on each of the three cards from two different credit companies. It gets really annoying as I like to make large gem purchases when I do decide to buy some and having to buy them 800 at a time over and over (when it allows) is making me not want to spend my money on this game when before I’ve been perfectly happy to support the game through large gem purchases in the past.