Mac App Store requires an active Internet connection in order to display software updates. If a client is in a closed network environment, you might see an alert message when trying to check for updates, "App Store cannot verify a secure connection with the App Store." Clicking Continue in this alert displays an Updates pane with no updates, and a message, "Cannot connect to the App Store."
To provide updates for Macs connected to a closed network:
- Configure a local Software Update server using OS X Server.
- Point your Macs to your Software Update server.
- Use the softwareupdate command line tool on each Mac client to install software updates.