If you receive a pop-up when trying to make a purchase, it means that there is an issue with your purchase.
This is usually due to a daily purchase limit on the Apple ID account and Apple will need to adjust this limit for a new transaction to happen. Otherwise, it should be reset in 24 hours.
For iOS devices, in-game purchases are made using your unique Apple ID and Password, and because iTunes processes all payments made for Catalyst Black, unfortunately, we are unable to help you with this issue.
For help, please contact iTunes Support.