A. 1. Check your internet connection: Ensure you have a stable Wi-Fi or mobile data connection. 2. Sync settings: Open Gmail, tap the menu icon, go to 'Settings', select your account, and ensure 'Sync Gmail' is checked.

B. 3. Clear app cache: Go to 'Settings' > 'Apps' > 'Gmail' > 'Storage' > 'Clear Cache'. 4. Remove and re-add your account: Go to 'Settings' > 'Accounts' > 'Google', select your account, and tap 'Remove Account'. Then, re-add it.