Fix Cloud AI Checkout

Our website offers a Cloud AI subscription, yet every attempted order fails right at checkout—the payment simply refuses to process. No charge ever reaches the gateway, and the user is left stuck on the final step.

Here is what I already know and need help with:
• Platform: website (built with standard HTML/CSS/JavaScript and a Stripe-based payment flow).
• Issue type: payment not processing.
• Moment of failure: the instant the customer clicks “Pay” on the checkout page.

I’m looking for someone to trace the error path, isolate the root cause—whether it lives in client-side scripts, backend API calls, webhooks, or misconfigured keys—and then implement a reliable fix. Afterward, please confirm the repair with at least two successful live-mode test transactions and submit a brief changelog so I can keep future deployments in sync.

Acceptance criteria
1. Checkout completes without errors; subscription status updates automatically.
2. Payment gateway dashboard reflects the new subscription in real time.
3. No personal data is logged to the console or server beyond necessary PCI-compliant details.

If you have solid experience with Stripe (or a comparable payment processor), webhook debugging, and subscription logic, you should find this straightforward. I can grant access to the repo, environment variables, and server logs the moment we begin.