How to show daily offline notifications in Android 10?

I can see one possible issue, and it’s possible to do this without the workmanager (assuming the device has a healthy connection at the time the notification runs).

Instead of doing your network in the receiver itself, I suggest starting a service (foreground service if above Android 8.0), and doing your work there. This is because android’s time limit for a receiver is much lower than a service/foreground service. So to me, it sounds plausible that your receiver is killed before the network request completes, and so no notification is shown.

You can show the notification in the service, and also schedule the next alarm since setExactAndAllowWhileIdle isn’t a repetitive alarm on it’s own. So in your receiver, something like:

@Override
public void onReceive(Context context, Intent intent) {
        Intent service = new Intent(context, BirthdayNotifyService.class);
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            context.startForegroundService(service);
        } else {
            context.startService(service);
        }
}

Then a possible service class:

public class BirthdayNotifyService extends IntentService {

    public BirthdayNotifyService() {
        super("BirthdayNotifyService");
    }

    @Override
    public int onStartCommand(@Nullable Intent intent, int flags, int startId) {
        super.onStartCommand(intent, flags, startId);
        return START_STICKY;
    }

    @Override
    protected void onHandleIntent(@Nullable Intent intent) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            //Build a simple notification to show if a foreground service is neccesary
            Notification noti = notiBuilder.build();
            startForeground(1, noti);
        }

        //Do your network request work here. After completed, show your birthday notification and stop the foreground service.
    }
}

To stop the service, right AFTER you display your notification for birthdays, use the following:

stopForeground(true);
stopSelf();

UPDATE: I used this method on my phone (Xiaomi Redmi Note 8 plus), it worked a few times but then stopped working. It works perfectly fine on stock android, but not on all devices. Therefore I would still say this is not a reliable solution to send notification on specific times.