Why don't push notifications come to Android after a while?

Question

Android

Please tell me about this situation.
There is a mobile app for Android. Users are sent invitations to events, and they receive push notifications.
The problem is that on devices where the application has been installed for a long time, push notifications do not come. If the application is installed recently - they come. If you reinstall, they start to come. But the new version, new assemblies were not created. Everything is as before.
What could be the problem? Has something happened to the tokens? Have they changed, become irrelevant? What could be causing this?

Answer 1

Expired tokens, they go bad over time. You need to update them periodically.