Can't purchase champion [CLIENT]

I have been trying to purchase a champion (Darius) with some IP. While the price for this champion is 4800 ip and I have 4860 ip, it doesn't seem to allow me to purchase it. In the shop it shows that I wouldn't have enough IP but when I go to the site where it shows the skins the champion has, it shows that I do indeed have enough IP. Once I try to purchase I will only get a message saying "Your purchase could not completed at this time." This isn't champion specific, though I have trie to buy other champions with the same price and the same problem repeats itself. Has anyone had this problem before and if so how did you solve it?