Did some of your Android users receive blank notifications?
In most of the cases, it happens because the Silent Push Notifications that MoEngage sends to track device uninstalls are not suitably handled on the App side for cases when Notification Display control lies with the App and not MoEngage.
To ensure if that's the case, test silent push notification as mentioned here.
When testing if the silent push notification is visible as a blank push notification, disable the Uninstall Tracking from the MoEngage dashboard. To disable, navigate to MoEngage Dashboard > Settings > App > Analytics and click on the relevant uninstall settings.
Second step is to handle Silent Push Notification as mentioned here . Once handled and all your users are on (or above) app version on which change has been implemented, you can enable the Uninstall tracking again by navigating to MoEngage Dashboard > Settings > App > Analytics.
Another reason why this happens is when your app is receiving notifications from multiple servers/providers or in-house notification services. Your users will receive Blank Notifications when if you don't handle push received from different servers correctly. Make sure the app does not try show notification if the notification is from MoEngage. Refer to Using your own listener service GCM or Using your own listener service FCM based on the library you are using.
If the problem still persists, please write to us at: firstname.lastname@example.org