If your automated WhatsApp messages reach guests in general — but one specific guest isn't getting them, even though the number looks correct and manual WhatsApp to them works — the cause is usually on the guest's side.
Most common cause: the guest's WhatsApp is out of date
Meta won't deliver WhatsApp template messages (the kind UpMarket sends automatically) to a guest whose WhatsApp app is outdated or on an unsupported version. Manual chat may still work while automated templates silently fail.
What to do: ask the guest to update WhatsApp to the latest version, then resend.
Other things to check
The guest's number is correct and in international format (e.g. +34612345678).
The property is Active (Properties → property → General Information → Active).
The relevant message is enabled (AI & Messaging → Automated Guest Messages).
The guest hasn't blocked the business number.
When it isn't something UpMarket can fix
If the guest is on an incompatible WhatsApp version, this is a Meta/WhatsApp limitation, not something UpMarket can override from our side. The fix has to happen on the guest's device (update the app), or reach them on another channel such as email.