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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.

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📱 Why can this happen?

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

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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.

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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.

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🧠 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