''Your Purchase Could Not Be Completed''

so recently i just bought an itunes gift card and i redeemed the code, and when i went to a game and i wanted to purchase an in app purchase i put in my password then a few seconds later a message popped up saying ''Your Purchase Could Not Be Completed, for assistance, contact iTunes support at ''www.apple.com/support/itunes/ww/'' if anyone can help me with this please do