Start with Twilio SMS → History when your customer says a message did not arrive. The module records its send attempt; Twilio’s later message status is separate evidence. A green result in the module does not by itself prove that the phone received a text.

Find the original attempt

1. Search History for the intended number or message text.
2. Filter by date, status and gateway.
3. Open the message and inspect its recipient, gateway, time, body, provider reference and error.
4. Confirm the attempt used Twilio rather than a Test / Debug rehearsal.

If no attempt appears, inspect the original trigger, category preference, phone source, queue timing and normal cron operation. The mobile source can be the standard client number or a nominated custom field; check the effective result and fallback in Health. A pending queued item may not yet have reached the provider.

Interpret the recorded result

Sent means the module received a successful initial provider result. Twilio can initially queue or accept a message and later report a delivery failure. If the immediate response already says failed or undelivered, the gateway records a failure and its available reason.

Failed calls for checking the recorded error and the specific account, credential, sender or destination condition it identifies. Unknown means the request timed out without a definite answer; it may already have reached Twilio and is not automatically retried. Reconcile that result before a manual repeat.

Correlate the Twilio message

Use the provider message SID from History to find the corresponding record in Twilio’s message logs. Review its current status and error details. The gateway does not continuously refresh the module’s History with later Twilio delivery updates. See Twilio’s message-status reference.

Check the intended From sender or Messaging Service pool, account restrictions, supported destination and recipient opt-out where relevant. Do not assume that changing the number or rotating credentials resolves every carrier refusal.

Keep the original reference and timing while your hosting team compares module History with the corresponding Twilio message record. Avoid repeated sends while the original outcome remains uncertain.

See the PD Twilio SMS WHMCS guide for related tasks, or explore PD Twilio SMS.