Fix Visa Slot API Errors

My application monitors U.S.-visa appointments and auto-books the first available time slot. Everything works except for two stubborn cities where no slots are ever returned. That tells me the trouble is buried in the backend API integration, not the UI or database.

Here is what I already have in place:

• A working PHP/Laravel backend that calls the external appointment-picking API.
• Proven logic that books successfully in every other city.
• Logging that shows the calls for the two problem cities complete, yet the JSON payload is empty.

What I need from you:

1. Trace and repair the API integration so the system can reliably surface and reserve slots in those two cities as it does everywhere else.
2. Identify whether the issue is with endpoints, headers, rate limits, hidden parameters, or anti-bot counter-measures, and patch accordingly.
3. Deliver clean, well-commented code plus a brief changelog so I can follow the fix. No broad rewrites—just a targeted, surgical upgrade.

Acceptance criteria:

• After your patch, calls to the external visa services API for the two cities return real-time slot data identical in structure to the functioning cities.
• Automated booking succeeds in a live test run (I’ll supply test credentials).
• No regression in existing functionality; all current cities must remain bookable.

This is my third attempt—two previous freelancers could not solve it—so please respond only if you have solid experience debugging live API traffic (curl, Postman, proxy tools), handling rate limits, and working with session-based auth tokens or hidden CSRF tricks.

Ready to bring in someone who can close this out quickly and cleanly.