Hi
For some reason in some phone I must restart the application so that the messages of firebasenotifications begin to arrive.
I have other phone that the messages come at once to run the application for the first time, but others I must restart the application and then everything works correctly. which may be?
When I started with FCM I had similar problems like you. Huawei had a whitelist. Only known apps were allowed to run in the background. Even WhatsApp did not show any notifications. You had to add it (see energy savings) to be allowed to run in the background by default.
What happens: Your app is fully stopped (and the FCM service, too) and can't receive any FCM messages. So add your app to the whitelist (options, energy savings...)