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> Fetch the complete documentation index at: https://moengage-doc-2298-s2s-type-case-sensitive.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-doc-2298-s2s-type-case-sensitive/Cpci9RABEv_ugaC3/images/moengage_06d833.png?fit=max&auto=format&n=Cpci9RABEv_ugaC3&q=85&s=afdc4712fb601d794788819c43802af7" 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-doc-2298-s2s-type-case-sensitive/vIMzIa9ro6mWcP-e/images/moengage_93aff4.png?fit=max&auto=format&n=vIMzIa9ro6mWcP-e&q=85&s=7159f4518c213ee22eb74bd8b893854f" 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.​​