Sometimes you have to relog before the bought items appear in your Item Mall storage. Also make sure the items you bought actually have a physical item (some AP items might be boosters or other stuff that don't actually appear in your Item Mall storage as an item.)
If you already checked the above stuff, and still didn't receive your items, send in an RT
under "Game Support" and make sure to include a link to a screenshot of your purchase log showing you bought the items. Good luck!