Hi again,
yes, as always with such things, it’s hard to tell why they don’t work since so many external systems are involved. Do you see new log lines getting added to the notifications.log file of your Mattermost server installation?
What mobile app version are you using on your android phone at the moment? Can you click on your profile picture at the bottom right, then on Settings and Notifications and on “Push Notifications”.
Try to toggle the settings there, ideally for testing purposes, turn notifications off completely, restart the app, set them to “Notify me about all new messages” then and make sure someone sends you a message to see if the notifications start working again.
If this is still not working, please also check your mobile OS settings with regards to the apps notification settings, maybe your app is not allowed to send you notifications or receive push settings? It’s worth a try to reset the notification settings for the Mattermost mobile application and see if that helps.