Fix WhatsApp API Phone Setup

I’m stuck connecting my phone number to Meta’s WhatsApp Business API. The number keeps showing as “unregistered” when I try to generate an access token, so I can’t move past verification.

Here’s what I need:
• Diagnose why the number fails during the access-token step.
• Walk me through—or directly handle—the correct sequence inside Meta Business Manager, Facebook Developer tools, and the Graph API.
• Complete whatever is required so the number is fully verified, registered, and able to send and receive messages via the WhatsApp Cloud API.

You should have hands-on experience with:
• Meta Business verification flows
• Phone-number onboarding for WhatsApp Business
• Access-token generation and permission scopes
• Troubleshooting unregistered or mismatched numbers

Deliverable: a working phone number on my account with a valid, testable access token and clear notes so I can repeat the process for future numbers.