ATSE is a new scan engine that uses a combination of pattern-based scanning and heuristic scanning to detect document exploits and other threats used in targeted attacks. Starting from SP2 of SMEX10.2, ATSE is integrated with SMEX and it’s later version.
The version comes with SMEX10.2 SP2 is 9.730.1020.
At the time this KB was created, there is no new version of ATSE. There is also no current ATSE version uploaded to the AU server. Thus, it is correct that ATSE shows as "Unreachable" on the SMEX web console.
When there is a new ATSE engine released, the new ATSE engine will then be uploaded to the AU Server and can be downloaded via active update, the message "Server Unreachable" will also disappear.