1. Check if you have Internet connection on your device
2. Ensure that the email app/client you’re using is up to date
3. Try to log in and out from the email account
4. Clear Cache and Data on the email client
5. Check for any setting to sync emails on multiple devices
6. Check if other clients are able to sync same email account
7. Try resetting your password
8. Try uninstalling and reinstalling the email client
9. Contact your email service provider for any issues.