I recently moved my Avast server from 2008 to 2012 on new hardware and all of the sudden I could not discover any clients using the LAN method. I made a quick assumption that it was server 2012 causing some sort of issue so I created a 2008r2 server just like it was previously on, re-installed however I get the problem. In looking at the server logs I am seeing “WNetOpenEnum failed with 0x0000003A error”. I have yet to discover or dig anything up on this issue.
According to this thread: https://forum.avast.com/index.php?topic=111084.0
You might want to check the logon credentials for the “avast! Enterprise Administration Server” Service