Why didn't a customer get an SMS?

The usual reasons a text didn't arrive — SMS not set up, the toggle off, no credits, the wrong plan, or an invalid number.

The usual causes, in order of likelihood: SMS isn't set up yet (or your venue is on the Free plan with no paid product — SMS is Available on Plus plan and above, and comes with any paid product); that particular message's SMS toggle is off in Settings → Customer notifications (or set to Ask and staff didn't tick it); your monthly SMS allowance ran out with no top-up credits; or the customer's phone number is missing, a landline, or invalid. Texts that fail for temporary reasons retry automatically for around two hours, and your credits are refunded if one ultimately can't send — that covers blips like the brief 5–10 minute outage while a sender-name change goes through. If the SMS card shows "SMS unavailable — please contact support", sending is paused until support fixes the connection. Related: How do I set up SMS messages?