Possible reasons include:
- Incorrect credentials or webhook UID.
- Unregistered DLT Template ID (for SMS) or WhatsApp Template Name.
- Missing user opt-in for notifications.
- Rate-limiting (one submission per IP per hour by default).
- Invalid mobile number format (must include country code, e.g., +919876543210).
Check Delivery Logs in your panel for error details and verify settings. Contact support for assistance.