If you experience issues with Gmail Offline, check for these issues and/or see Google’s Troubleshooting.

Troubleshooting

Logging Out Removes Data

Logging out of your Google Accounts removes your offline gmail content, so if you enable gmail offline, allow your data to sync, log out, and then try to access Gmail without an internet connection, it will not work. If you log out of your account, you'll need allow your data to resync when you log back in and have an internet connection. 

Old Offline Chrome App

• If you have the old Gmail Offline Chrome App at chrome://apps/, uninstall it prior to enabling offline mail in Gmail Settings
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• If you already enabled offline in Gmail but are having issues and realize you have the old Gmail Offline Chrome app, uninstall Gmail Offline in Gmail, uninstall the Chrome App, and then re-enable Gmail Offline in Gmail

Gmail in Only One Tab

• Gmail can only be open in one tab (when enabling, bookmarking, and accessing offline) for offline to work correctly
• If you have more than one tab open, close all but one Gmail tab and then try enabling Gmail offline, bookmarking Gmail, or accessing Gmail when offline again

Google’s Gmail Offline Troubleshooting for Admins

Google’s Gmail Offline Troubleshooting