1
You did not mention anything about the payment module you are using.So I assume you are using a payment module name
"Abc_PaymentModule". I also assume in that payment module there is a controller which is handling the response back from payment gateway. It seems you are getting Form-Key error due to CSRF (Cross-Site Request Forgery) tokens on form POST ...
Only top voted, non community-wiki answers of a minimum length are eligible
