How do I purchase a bag of gems from Clash of Clans?

Question

I just put 10$ in my apple account. I had 21 cents prior, my total is $10.21 now.
The bag of gems (1200 gems) is 9.99
I have enough money to purchase this bag of gems from Clash of Clans.
I press 'Bag of Gems -1200-' and it goes black and white then gives me a box that says 'Confirm Your In-App Purchase'
I press 'Buy' because yes I want to buy this bag of gems.
Then it gives me a window that says 'Insufficient Store Credit Remaining' and redirects me to the payment-method page
Where I sign in, confirm that it's a gift code and that I do in fact have enough store credit remaining
To which is remains adament in telling me I don't.
Someone please tell me whats going on before I rip my hair out.

Answer 1

You may also have to pay applicable sales tax on the in-App purchase.