If this message pops up:
"Insufficient Remaining Store Credit. Tap Continue to sign in."
This means that your balance in the App Store is insufficient to complete the process; enter your password, then click on continue to log in and follow the instructions.
For example:
If your store balance is 5$ and you want to buy a package worth 5$, you will get this message because there are taxes imposed by Apple and the store's country on the pack's final price.
"Insufficient Remaining Store Credit. Tap Continue to sign in."
This means that your balance in the App Store is insufficient to complete the process; enter your password, then click on continue to log in and follow the instructions.
For example:
If your store balance is 5$ and you want to buy a package worth 5$, you will get this message because there are taxes imposed by Apple and the store's country on the pack's final price.