Start with one affected message
Choose one failed recipient and one successful recipient from the same campaign, if available. Compare the sending number, template, language, send time and latest status. Use internal record IDs in your investigation; redact phone numbers from shared screenshots.
If every message stopped before sending, inspect the campaign or connected number. If only some failed, inspect their individual results. A campaign summary hides these differences.
Business app: check the app's current broadcast requirements and the recipient relationship. Business Platform/API: use message IDs, delivery callbacks and provider errors. Advice about app broadcast lists does not diagnose an API queue.