> ## Documentation Index
> Fetch the complete documentation index at: https://moengage-gr001-flows-limits.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# 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-gr001-flows-limits/c5R8t2JnENFnJPp_/images/moengage_06d833.png?fit=max&auto=format&n=c5R8t2JnENFnJPp_&q=85&s=beb6da9a4567c0d482cc1a48b73be3cf" 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-gr001-flows-limits/yw2KBnk1D0iLfzcH/images/moengage_93aff4.png?fit=max&auto=format&n=yw2KBnk1D0iLfzcH&q=85&s=00b813496d98643785c8a8621a816beb" 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.​​