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.

Check whether the text was delivered

Open the booking: each text line (booking confirmation, reminder, cancellation, no-show) shows what the mobile network reported — Delivered, Failed with the reason in everyday words (for example "Number not in service" or "Phone switched off or out of signal"), or Sent · waiting while the report is on its way. Activity log → SMS shows the same for every text, and Rezo can check it for you too.

• Delivered — it reached the customer's phone. If they can't find it, ask them to check their messages from your sender name.
• Failed — it didn't arrive. If it failed before leaving our text service, its credit is returned to you automatically. If the mobile network accepted it but couldn't deliver it (the phone was off for days, the number is no longer in service, or the network's spam filter stopped it), the credit stays used — the network still charges for a text it accepted. Check the number with the customer and resend from the booking.
• Sent · waiting — no report yet. Most arrive within seconds; a phone that's switched off can take up to three days before the network gives up.

Related: How do I set up SMS messages?