Purchase credit (for regular Users) not working?

I have enabled Credit system in my plugin. The add/remove features work fine in the admin side. For regular users, the ‘Account Balance’ loads properly. However after selecting a credit plan and clicking the Continue button, the page simply reloads for me. The documentation at http://awpcp.com/documentation/#credit-system says that the payment methods will be initiated once the user chooses a credit plan. Please let me know if any missing configurations lead to this issue.

https://wordpress.org/plugins/another-wordpress-classifieds-plugin/