On MainWP > Sites > Manage tab the Status column shows you the current status of your websites:
- The dark green icon with a number will show you the number of available updates on your site.
- The red exclamation mark indicates that the site is down.
- The green checkmark icon indicates that your site is online.
Also, your Status column can show you this icons:
- The red plugin icons indicates that site is disconnected from dashboard.
- The yellow radiation icon indicates a plugin or theme conflict.