Game of war unable to make purchases using new Apple ID

What happens when you to try to the IAPs, and have you created a new account or updated your existing account to have a new primary email address ?

If you've created a new account then you will have to delete and rebuy/download the app to be able to do in-app purchases with that account - all apps (and any other content from the store) are tied to the account that downloaded them, only that account can do IAPs.

If you've updated your existing account then try logging out of the account by tapping on your id in Settings > iTunes & App Store on your device and then log back in with the updated version of the account and see if you can then do IAPs.