After upgrading to Advanced Threat Protection 3.0.5, the ATP web interface no longer shows the Appliances page on the sidbar and there is a System Health error regarding retrieving component health status.
There was an issue identified in the migration of data to the 3.0.5 version. This is has been fixed with some additional clean-up scripts.
This is resolved in ATP 3.1. If you cannot upgrade from the web interface, you will need to use the 'update' command on the CLI.