Steam App Wont Open. Choose Security & Privacy under System Preferences. steam client won't open - This happens occasionally and a restart should be enough. You can temporarily disable your antivirus and check if the problem persists.
The exact same thing occurs when running in administrator mode. I tried starting it manually or as an administrator and from start>all programs, and it still wont work. Make sure that your installation is intact.
This solution requires ample time so only start when you are sure that your PC won't be interrupted.
The problem could be due to missing or corrupt files in the SteamVR app.
Check whether Steam won't open on Windows again. Clean Boot can help identify if third-party apps and Steam won't open from taskbar for several third-party programs that might interfere with it. Whenever I try to open steam all that happens is the steam icon bounces on the bottom of the screen indefinitely.