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description: Reasons due to which your app push campaign may go undelivered.
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# Why App Push Notification may not get delivered?

There are several reasons for which you may not be able to deliver your App Push Notifications

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* **Frequency Caps:** This failure occurs when the frequency cap limit is exhausted. It depends on parameters that are measured daily, weekly, monthly, or over a lifetime. Users whose frequency cap value is >0 will receive your engagement. To learn more about Frequency Caps, click [here](../../getting-started#frequency-caps).
* **Personalization Failure:** This failure indicates that the engagement failed to send while replacing the personalizing parameters with the actual value stored in the users profile.\
  **Use Case:** Suppose there is a user in a segment with no premium amount registered. You create engagement for that segment of users using a premium amount macro with an expiration date. The user with no registered amount will not receive the engagement as that parameter does not exist in his/her stored profile.
* **FCM Failure:** The number of notifications meant to be delivered successfully by Lemnisk, but failed due to FCM (Firebase Cloud Messaging) failure.
* **FCM/APNS Configuration Issue:** This error arises when app configuration is disabled for push notifications, the APNS certificate is not generated or the FCM configuration is incorrect.
* **Unsubscribed:** This indicates that the user has unsubscribed from receiving push notifications from your app.
* **Not Delivered:** This failure comes when the message is sent successfully from FCM server but the notification was not delivered to the end user. There are multiple reasons why this may happpen:&#x20;
  * **Network related issues:** To deliver Push Notification, the device must have a proper internet connection. Intermittent network connection often leads to non deliverability of app push notifications.
  * **DND:** If the users have put the phone on DND mode, the push notification will not be delivered to the end user even after FCM sends success.
  * **OEM-related issues:** Push notification delivery on Android devices can be impacted by background process restrictions implemented by certain manufacturers. This is especially evident among Chinese OEMs that modify the Android OS to optimize battery life. Many of these devices have a battery-saving feature that aggressively shuts down apps when not in use, resulting in missed notifications for users. As per the industry, this is by far one of the most important reason for low deliverability of push notifications in South Asian countries like India because they're heavily dominated by Chinese OEMs.
* **Uninstalled:** This indicates that the user uninstalled your app for which the push notification cannot be delivered.
* **Others:** This includes all the other reasons for which the APN was not delivered such as system failure, server crash, campaign failure, etc.
