Android Tutorial FCM messages checklist (prevent issues)

With newer Android versions came more options for power saving and permissions we have to deal with. There are a lot of threads about FCM messages not arriving or beeing delayed. Here's a small "checklist" which may help. Feel free to add the list.

Before installing your app

- send data messages (see examples in the forum or Google docs) only as those message types are delivered in the background
- set the priority to "high"
- use NB6 to create your notifications and set the priority to "high", too
- did you (more precise: your phone) restrict any network traffic, apps running in background, etc.?

After installing your app / first run

Go to app settings (shortcut is to long click on the app's icon) and check the following:

- Autostart -> ON
- Restrict data usage -> OFF (otherwise the network connection is cut off when your phone sleeps)
- Notifications -> all ON (there are "profiles" containing the settings like vibrate, sound, light, where to show, too. These come from the NB6 settings)
- Run in background (mostly "energy saving plan" or similar) -> YES (or not restricted)
- Compare your app's setting with e.g. the one of WhatsAPP

My old Huawei P10 had a whitelist with apps allowed to run in the background. WhatsApp wasn't initially in that list which - guess what - caused it to be stopped when the phone went to sleep. As a result no notifications were showed. I had to change the settings manually. Later Huawei did an update and added WhatsApp to the whitelist.

Still having issues?

- send a timestamp with the FCM message
- when receiving the message add the actual timestamp to the notification text to compare
- mostly the message IS received but the notification isn't thrown. Here check the app settings again (see above).
- if a notification isn't thrown when the phone sleeps, check the permissions/powersettings again (message arives but due to the settings it only shows when you wake up the phone)
- Is your internet connection stable? On Wifi: Does your router disconnect when there is "no" traffic?


Even today WhatsApp (or Android/Google?) is having issues sometimes. From time to time I have new messages without a notification or without sound/vibration. Google is handling billions of messages every day.