Account Balance

Today i buyed an xbox gift card for 15 euro. I typed the code everything was ok. It said to me that it charged to my account 15€ everything ok. Now i wanted to buy the gta iv game because i saw that its now for sale and it showed me that i have no money
on my account then i go to fortnite a d it showed me normaly that i have the 15€ that i typed in. Then i go back to microsoft shop and it still shows me i have no money. But why? I really want to play gta iv i would appreciate an answer.

:)