Xbox live Gold

My son wants to buy one month of Xbox Live Gold. It says "You need a parent to buy this. We can't send a request for this one, so you'll have to ask them another way. We find a hug and a please works wonders!" I made sure there is enough money on his account
but it doesn't help. We switched to my profile and I bought it and paid for it but when my son logs in, he can't use it. What can we do?

:)