WHMCS Tags payment-gateways Modules in WHMCS use templates to define what users see. You can customize these module templates using WHMCS's overrides system. Troubleshoot and resolve processing issues that did not result in a log entry. Troubleshoot and resolve an Oops Error: Module Not Found error. Troubleshoot and resolve Gateway Activation Failed errors while attempting to activate PayPal Payments. Troubleshoot and resolve problems due to PayPal® Instant Payment Notification (IPN) failures. PayPal payment gateways may generate specific subscription log entries. After attempting to migrate to the new PayPal Payments payment gateway module from a previous PayPal® module, you are experiencing problems with subscriptions.