Child cannot use credit to purchase minecoin

I have a child as part of my Microsoft family. On that account, they must ask any time they want to purchase something. I gave one child a $10 credit to use when they see fit.

Family / Child computer

1. In Minecraft Windows 10 Edition, click on the coin in the top right to purchase more coins. Currently a credit of 40 coins so it worked before.
2. Click on the $5.99 option to purchase more coins.
3. Click ask for permission to purchase coins.

Go to parent computer

4. Click Allow the purchasing of the minecoins.

*** Get prompted to add funds to the account.

There already is a $10 credit on the account, why can't I use that?

5. Call Microsoft and try and get them to help out why I can't use the credit. They couldn't figure it out. I was on the phone with them for an hour.
6. Call again to ask for a refund.

--- Refunds are not available for credits.

I have no idea what to do now. Microsoft has $10 I can no longer get back, nor use.