Urgent: Credit/Debit Card Transaction Failure

I am currently facing an urgent issue with my payment processing system. Transactions are failing during the payment processing stage, specifically when using Credit/Debit Cards.

Key Requirements:
- Diagnose and fix transaction failures occurring during payment processing
- Ensure Credit/Debit Card payments are functioning properly
- Conduct thorough testing to prevent future issues

Ideal Skills:
- Extensive experience in payment gateway troubleshooting
- Proficient in eCommerce and online transaction systems
- Prior experience with Credit/Debit Card processing issues