Make sure to troubleshoot and resolve any issues with payment gateways, payments, currencies, or related features as soon as possible. WHMCS includes several supported payment gateway modules for accepting payments through PayPal®, including the new PayPal Payments gateway. Disputes, including chargebacks, inquiries, or retrievals, occur when a client contests charges that you collected from their card issuer. Troubleshoot and resolve issues with DUPLICATE_INVOICE_ID errors. Troubleshoot and resolve issues with login credentials for your payment gateway. Troubleshoot and resolve the ionCube Encoder® error that makes the Admin Area return HTTP 500 after you update WHMCS. Troubleshoot and resolve problems with PayPal® payments that succeeded in your PayPal account but that do not appear in WHMCS. Troubleshoot and resolve problems with missing PayPal® subscriptions. Troubleshoot and resolve warnings about the OPcache PHP extension. Troubleshoot and resolve problems with orphaned PayPal® subscriptions. Troubleshoot and resolve No Local Credit Card Payment Gateways Enabled errors while using the PayFlow Pro or PayPal Pro Reference Payments payment gateway modules. Troubleshoot and resolve Details could not be saved. Remote storage failed errors while using the PayFlow Pro or PayPal Pro Reference Payments payment gateway modules. Troubleshoot and resolve problems due to PayPal® Instant Payment Notification (IPN) failures. PayPal® payment gateways may generate specific subscription log entries. Troubleshoot and resolve Referenced transaction or order is too old errors while using a PayPal payment gateway module. Troubleshoot and resolve L_SHORTMESSAGE0 => Security error errors while using a PayPal payment gateway module. Troubleshoot and resolve PayPal connection errors. Troubleshoot and resolve Transaction ID already exists errors for PayPal Payments transactions. The PayPal Transaction Lookup addon module displays your PayPal® merchant account balance on the Admin Dashboard and lets you search PayPal transactions without logging in to PayPal. Troubleshoot and resolve issues that cause Invalid Receiver emails while using a PayPal payment gateway module.