> ## Documentation Index
> Fetch the complete documentation index at: https://help.treble.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Failure by unable to contact in WhatsApp

> Description of the `FAILURE_BY_UNABLE_TO_CONTACT` error shown in WhatsApp reports.

This status indicates that **WhatsApp could not deliver the message at that specific moment**, because it did not find a user device that could **receive and process that type of message correctly**.

👉 **It does not mean** that:

* The number is invalid
* The user has blocked you
* There is an error in your account or configuration

It is a **temporary failure**. This status message can be confusing, but in the vast majority of cases **it does not indicate a serious problem nor requires action on your part**.

***

## 📱 Why can this happen?

This status usually appears in normal WhatsApp usage situations, for example:

### 1. The user is using WhatsApp Web

Some messages (such as buttons, lists, flows, or new features) **are only available on mobile WhatsApp**.

If the user:

* Is active on WhatsApp Web
* But their phone is not available (turned off, no internet, in background)

WhatsApp cannot deliver the message at that moment.

***

### 2. The user's WhatsApp app is not updated

Some new features require recent versions of WhatsApp.

If the message uses a newer functionality than the user's installed version:

* The message cannot be displayed yet
* WhatsApp marks the attempt as temporarily undelivered

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### 3. Temporary connection issues

It can also occur if:

* The phone has no signal or no internet
* The device is turned off
* The system closed WhatsApp to save battery

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## ⏳ Why can the message appear as `delivered` later?

WhatsApp **automatically retries delivery**.

When the user:

* Opens WhatsApp on their phone
* Updates the app
* Recovers internet connection

The message can be delivered correctly and change its status to:

✅ **`delivered` (delivered)**

This is **completely normal** and expected.

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## 🧘‍♂️ Should I worry if I see this status?

**No.**

Recommendations:

* It is not necessary to resend the message immediately
* It does not indicate a permanent error
* It does not affect the conversation or the end user

In most cases, the message is delivered just a few minutes or hours later.

***

## 🧠 Quick summary

* `FAILURE_BY_UNABLE_TO_CONTACT` = **temporary** failure, not definitive
* Usually occurs due to WhatsApp Web usage, old versions, or momentary lack of connection
* WhatsApp automatically retries delivery
* It is normal for the message to end up as **`delivered`** later