> ## Documentation Index
> Fetch the complete documentation index at: https://moengage-sdk-deprecated-versions-all-platforms.mintlify.site/llms.txt
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# Why Do Push Notification Tests Often Fail for Mobile Numbers?

> Resolve push notification test failures when using mobile numbers by switching to the unique user ID field to identify reachable users instead.

## Problem

When attempting to send a test push notification campaign, the notification fails, and the following message is displayed:

Installed User not found for Mobile Number = 0000000000

<img src="https://mintcdn.com/moengage-sdk-deprecated-versions-all-platforms/dYKWhmtzDbZP5dWp/images/moengage_06d833.png?fit=max&auto=format&n=dYKWhmtzDbZP5dWp&q=85&s=94f6e3efb00d0d5ba59abc3eb507e30c" width="556" height="304" data-path="images/moengage_06d833.png" />

## Solution

* Use the unique ID field of reachable user instead of the Mobile Number attribute to ensure push notifications are sent.
* The unique ID field can be found in the user profile with the name **ID**.
  <img src="https://mintcdn.com/moengage-sdk-deprecated-versions-all-platforms/tBOqttMLA8XHICm2/images/moengage_93aff4.png?fit=max&auto=format&n=tBOqttMLA8XHICm2&q=85&s=ead9772b73295d38b07d5e0954bbaa96" width="1600" height="275" data-path="images/moengage_93aff4.png" />
* The unique ID is unique to each user and is used to determine whether the user can receive push notifications.​​