Why are push notifications not being received by a specific User ID, even though the system indicates they were sent?

If push notifications sent to a specific User ID aren't arriving on the intended device(s), especially test devices, it might be due to the device registration limit associated with that User ID.

Here’s how to troubleshoot and resolve this:

1. Check the Device Limit: A single User ID can be linked to a maximum of 21 unique devices (HWIDs) in Pushwoosh. Testers or developers who frequently reinstall apps on various devices can sometimes hit this limit.
2. Verify Associated Devices: Check how many devices are currently associated with the specific User ID in your Pushwoosh Control Panel or via API methods.
3. Clean Up Stale Devices (If Limit Reached): If the 21-device limit has been reached, or if there are many old/inactive devices linked to the User ID, you must remove some before new ones can be registered. You can:
   • Delete specific, inactive device records using their HWID via the /deleteDevice API method.
   • Unlink devices from the User ID (e.g., by registering the device again without associating the User ID).
4. Re-register the Target Device: Once you've ensured the User ID is below the device limit, the most reliable way to ensure the target device is correctly registered is:
   • Completely uninstall your application from the target device.
   • Reinstall the application.
   • Launch the app and log in or perform the action that assigns the User ID to this specific app installation.
5. Verify and Test: After reinstallation, check your Pushwoosh data to confirm the device's HWID is now correctly associated with the User ID. Send a test push specifically to this User ID or HWID to confirm notifications are being received.

Important Note: Pushwoosh sends notifications to the platform's gateway (APNS for iOS, FCM for Android). While Pushwoosh confirms the handoff to the gateway, final delivery depends on the gateway service and the device's status (network connectivity, battery optimization settings, app notification permissions).