Fix Apple Pay Subscription for iOS app

My Swift-based iOS app already presents Apple Pay and collects payment details, but once the user completes checkout a recurring subscription never activates. I can replicate the problem every time on TestFlight and in the sandbox, so the issue is clearly lurking in my implementation rather than Apple’s back-end.

Here is what you will step into:
• StoreKit 2 code is in place and compiles cleanly.
• Apple Pay sheet shows, tokenizes the card and apparently charges it.
• I have only partially implemented server-side receipt validation, so that may be where the workflow breaks.

What I need during a screenshare session (Zoom or Google Meet—your choice) is:
1. Watch the live failure with me, inspect the logs, and pinpoint why the post-payment callback isn’t flipping the subscription to active.
2. Patch the Swift code or the server script so that the recurring plan starts immediately after a successful charge.
3. Walk me through any missing or misconfigured receipt validation steps so I can maintain them going forward.

We will test together in the sandbox, then push a TestFlight build to confirm everything works end-to-end. Once the subscription status flips correctly and renewals appear in App Store Connect, we are done.

Please be comfortable with Xcode, StoreKit 2, Apple Pay, and server receipt verification. A concise fix and clear explanation are all I’m looking for.