Start in your Audit Log, under Reports, with Messages chosen in the Event box, and find that customer. What it says against their card tells you which of these it is.
1. They were not in the group
If they are not on the list at all, the group you chose did not include them. Check what you picked: "customers with at least 5 stamps" leaves out everybody on four.
2. The daily limit applied
If it says the card was updated because of the daily limit, they had already been notified in the last 24 hours. The message is on their card and they can read it now. Send the next one a day apart.
3. They have not added the card to a wallet
If it says no wallet pass yet, they are using the card in their browser. There is nothing to notify. Help them add it and the next message reaches them properly.
4. Their phone chose not to show it
If it says a notification was requested and they still saw nothing, the phone decided. A phone that is off, out of signal, on silent, or has notifications turned off for wallet cards will show nothing and tell nobody. Ask the customer to open their card: your message is on it.
If the wallet was not reachable
That means the wallet refused or could not be contacted at that moment. The message is still stored on the card, so it appears the next time the card updates, which for an active customer is their next stamp. If you see this against most of a send rather than one or two, email us and quote the date of the message.
Whatever happened, the message itself is on the customer’s card. Nothing is lost, and asking them to open the card is a real answer rather than a fob-off.