This happens when Google detects that you have more accounts that you own or on the device, generally linked to the Google store. Please follow these steps to change your Google account for in-app purchases:

Add the account you need to your device (Settings -> Google -> Account -> Add account)

Delete the app.

Go to the browser version of the Google Play store.

Check the Account tab in the Google Play menu to make sure you've logged into the right Google account.

Find the app and install it.

Open the app and you should now have your correct account in the game, therefore your original game account. You mustn't OPEN MORE gaming ACCOUNTS, to prevent this from happening more often.