A. 1. Check notification settings: Go to 'Settings' > 'Apps' > 'Gmail' > 'Notifications' and ensure notifications are enabled. 2. Disable battery optimization: Go to 'Settings' > 'Battery' > 'Battery Optimization', find Gmail, and select 'Don't optimize'.

B. 3. Clear app cache: Go to 'Settings' > 'Apps' > 'Gmail' > 'Storage' > 'Clear Cache'.