I’m running version 1.5.4 of Atom and on OS X 10.11.3.
I have downloaded, redownloaded and then downloaded again from atom.io, tried it from the applications folder and the download folder.
When I double click to launch the app nothing happens.
Checking console it tells me
Mar 11 16:11:19 W21297 com.apple.xpc.launchd (com.github.atom.65952): Service exited due to signal: Killed: 9
Any ideas what could be causing this?