Malphite can't max R at lvl 18 when using ancient coin line

This bug has happened to me twice. I play Malphite support and have recently started taking ancient coin for the extra mana sustain early game. If the game goes long enough to reach lvl 18 it will bring up the buttons to level his abilities, but they will all be dark and unclickable. I haven't had this happen with any other champion.