How to resolve Failed Messages in WhatSender?

This tutorial is designed to assist you in case you encounter failed messages when sending. You can easily detect these failures by reviewing the history tab for each of your deliveries.

In the summary, you will see the following:

- All messages sent (marked in green, indicating they were sent successfully).
- Some failed messages (some in green and others in red).
- All failed messages (all in red).

There is no need to provide solutions for messages sent successfully. Below, we will provide solutions for the other two situations.

SOME messages have failed

This can be due to the following reasons:

Cause 1: The number is incorrect or does not have WhatsApp associated.


Unfortunately, there is no way to fix it. It is common to encounter this situation when acquiring a database through advertising, as many clients do not provide their real number and choose to enter a fake one. If the phone number is incorrect or does not have WhatsApp associated, Whatsender will identify it as failed.

Cause 2: The number format is incorrect.

If you are sending messages to different countries, it is important to pay attention and include the corresponding country code. For example:

  • For Colombia, the number should include the country code 57: 573235997687.
  • For Spain, the number should include the country code 34: 34674872985.

It is important to note that numbers should not be separated by spaces or contain parentheses or other signs. If your number includes any other symbol other than a digit, Whatsender will mark it as an error. Therefore, it is essential to clean your database before copying it into Whatsender.

Additionally, it is important to conduct a small investigation on Google to validate the correct dialing when sending messages to other countries.

For example:

In Mexico, until before 2020, it was necessary to place a 1 in mobile numbers when making calls, but it was not necessary when sending messages via WhatsApp. This means that in your database for sending messages through Whatsender, the number was registered as 522281938793, while to make a call, the format 5212281938793 was used.

This distinction between the format for calling and sending messages is still valid in many countries around the world. Therefore, we recommend that if you are sending messages to foreign countries, you familiarize yourself with the correct format and the number of digits the number should have to avoid it being marked as failed.

Resolve any formatting issues you have encountered and resend your messages.

Cause 3: WhatsApp temporarily does not recognize that number.

WhatsApp carries out updates continuously, and it is common for these changes to be implemented in some countries or regions before others. This discrepancy in updates can cause a number to which you have previously sent messages to appear as failed on occasion. This can happen because the WhatsApp API does not recognize it, either because your version of WhatsApp is not updated or the receiver's. Therefore, it is important to always keep the WhatsApp application on your phone updated to prevent you from being the cause of the problem.

Generally, this issue can be resolved in a few hours or even days. If it persists, the solution is to try again at another time. To do this, you can go to the history tab, find the message delivery that had the error and click on "Retry." This way, the message will be sent only to the numbers that failed previously. You can explore all the functionalities of the history tab in this guide.

It is essential to remember that if the numbers fall under causes 1 and 2, they will continue to fail even after retrying the delivery. (Retry button)

Cause 4: Slow connection

If after checking all the possible previous causes, you still experience message sending failures, the reason may be a slow connection. In this case, the first thing you should do is verify that you have not modified the error timeout parameters. By default, this timeout is usually set to 5 seconds.

We recommend not reducing this timeout. However, if you have done so, you can use the "reset config." button and then try sending again. If the failures persist, an option is to increase the timeout to a maximum of 10 seconds. We suggest performing incremental tests until you find the appropriate time for your connection.

ALL messages are failed

Cause 1: Incorrect prefix assignment

If you are sending messages to the same country, you have the option to select a generic prefix. This setting is available in the "Profile" tab of the Whatsender extension.

If you use this option, you must be careful to remove the prefix from your numbers because it would be duplicated. For example, let's say you set the general prefix for Colombia as +57. Then, your numbers that you would paste into Whatsender would look like this:

3235997687
3217895250
3249381437
etc.

If you want to manually add the prefix, it would look like this:

573235997687
573217895250
573249381437

As you can see, you will need to remove the spaces between numbers and the + sign and space between the numbers. It should not have any strange symbols.

CAUSE 2: Hidden error in number format

If you are importing your contacts from an Excel file, we recommend converting them to CSV format. Even if you are just copying and pasting contacts, this is important. The reason is that by changing the file format, you will be able to identify if the number contains characters other than numbers, such as underscores (_) or other non-numeric characters. In such a case, you will need to remove all this additional information and leave only the numbers, without spaces, as explained above. This way, you will avoid errors such as incorrect numbers or pending messages.


This tutorial has been effective for 99% of people who have faced this problem. However, if you find yourself in that 1% who have not been successful, we would be happy to assist you through our contact form.

When describing your problem, please include all relevant details, such as if you are sending attachments. Additionally, if you trust us, it would be helpful to provide the database in Excel format so that we can rule out any possible errors related to the format of the numbers in the file. Please note that we will only use this information for the purpose of providing customer support.