Your Android operating system kills the app while it is in background.
Check battery settings for the app - it should be set to Unrestricted.
For some devices, there may be additional options to prevent the app from being killed - e.g., on Xiaomi you need to enable Auto Start setting for the app. Please consult https://dontkillmyapp.com site for any additional settings for your device.
-iOS notifications failed to initialize correctly
+Why my notifications aren't working on iOS
Check the color of the bolt icon next to Notifications in app settings - it should be green.
If it's not, please open notifications, disable them (choose Off / Local), and then enable again - you should do it when you have Internet connection.
+Check if your push server has been restarted at time of the issue (Notifications -> Push server) at https://status.simplex.chat if it has been restarted, you may not receive notifications from that time.
+If device was offline, you may need to open the app to start receiving notifications.
If the above didn't help, the reason could be that iOS failed to issue notification token - we have seen this issue several times. In this case, restarting the whole device should help.
+In some cases notifications may still not work, iOS notifications are hard to do right in a decentralized app, we will be improving them soon to be more reliable.
Messaging server or notification server is under maintenance
Please check the current status of preset servers at https://status.simplex.chat. You can also connect to status bot via QR code on that page - it will send the updates when the server is offline for maintenance, and also when the new versions of the app are released.