The short answer
Every text that fails posts one line saying why, beginning "Message to (number) failed." The line is chosen from the carrier's own code, so it says whose side the problem is on and what to do. The full list:
| The line after "Message to (number) failed." | What it means | Whose side |
|---|---|---|
| That number cannot receive texts. It may be a landline or the wrong number. | The number has no texting service, or a digit is wrong. Call it, or check the number. | The recipient |
| That number is no longer in service. | The number has been disconnected. | The recipient |
| The recipient’s phone could not be reached. Try again in a few minutes. | The phone was off or out of coverage, or their carrier had a moment. Send again later. | The recipient, temporary |
| The recipient’s phone refused it. They may have blocked this number. | Their handset or carrier turned it away. | The recipient |
| This person opted out of texts from your number by replying STOP. They can text START to opt back in. | Their choice, and it is honored automatically. Only they can undo it, by texting START. | The recipient’s choice |
| It was too long. Split it into shorter messages and try again. | The message exceeded what a text can carry. | The message |
| The attachment is too large or not a supported type. Try a smaller picture or a link. | Picture messages have size and type limits. | The message |
| The recipient’s carrier filtered it as spam. Avoid link shorteners and all caps. | The wording, the links, or the volume looked like spam to their carrier. Plain words, full links, one at a time. | The message |
| Your number reached the carrier’s daily sending limit. Wait before sending more. | The number sent more today than the carrier allows. If you send in bulk regularly, ask us about the right setup. | Volume from your number |
| Texting outside the US and Canada is not available on this number. | International texting is not offered on the number. Ask us if you need it. | Not offered |
| Texts to short codes and toll-free numbers cannot be sent from this number. | Five-digit codes and 800-type numbers are not reachable from a business number. | Not offered |
| Too many recipients for one text. | A group text has a limit on how many numbers it can hold. | The message |
| Your number is not registered for texting yet. Registration is in progress. | The carrier registration has not finished attaching the number. Receiving works; sending starts when it clears. | Ours, in progress |
| Your number is not set up for texting. To set it up, contact support. | The number was never registered, or its registration needs a person to look at it. | Ours |
| The carrier did not accept it from your number. Try again in a few minutes. If this keeps happening, contact support so we can fix it. | The number is registered on both sides and the carrier still refused it. Once is a blip; a repeat is a carrier record we chase for you. | The carrier |
| Try again in a few minutes. If this keeps happening, contact support. | A reason the carrier did not name. We read the code when you tell us. | Unknown until we look |
What "sent" means
A text carries no delivery receipt from anybody. "Sent" means the carrier took it, and nothing on our side or theirs confirms it arrived; a message that vanishes with no failure line most likely did arrive. WhatsApp is different: it reports delivered, failed, or read.
A pattern, not a single failure
One "could not be reached" is a phone that was off. Every text to one carrier failing for a day is worth telling us about, and every text from your number failing is either registration (see 10DLC registration) or a carrier record we chase on your behalf. Complaints about unwanted texts also feed the filters, which is why a text blast done wrong can break the texting you rely on.
Where to read it
In the portal's Messaging inbox, under the message. In Webex, as a line in the customer's space. On a number that texts by email, as an email back to the sender. The office sees the same line, so quoting it to us is the fastest start.