Incomplete Minecoin Purchase and failure to restore previous purchases

My son was trying to purchase some additional minecoins on my iPad Air 2 (using my apple account). I approved the purchase (entered apple password) but the transaction failed. Each subsequent time we have tried to complete the purchase we receive an error stating:

"Incomplete minecoin purchase: Someone started a purchase with the billing account on this device. Would you like to complete the purchase with this account?" [See attachment 1]

When I choose "yes" I get the following message: "Something Went Wrong: We were unable to connect to the app store. Try signing in to the app store or checking your internet connection." [See attachment 2]

I am connected to the internet, and have access to the app store. And unfortunately, when I tried to delete and restore the app, the "RESTORE PURCHASES" function does nothing and my son cannot access his previously purchases templates (x2) and coins (380 remaining).