WHMCS Troubleshooting Troubleshoot Payments Troubleshoot and resolve an Oops Error: Module Not Found error. 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. Troubleshoot and resolve PayPal connection errors. Troubleshoot and resolve Transaction ID already exists errors for PayPal Payments transactions. Troubleshoot and resolve Remote Transaction Failure. Please Contact Support. errors.