I need an experienced CodeIgniter developer to fix a payment gateway integration issue on an existing Codecanyon script (Affiliate Management System). The payment gateway (PayFast) worked previously but now fails with an "Authentication error" after a script upgrade. Requirements: - Expertise in CodeIgniter 3 - Experience with PayFast integration - Ability to troubleshoot and resolve authentication errors - Work must be done in the production environment Please only apply if you have relevant experience and can ensure a smooth, secure fix.