How to resolve issue of help shortcut key (Cmd + Shift + /) not working? I really like the shortcut key to bring up the help menu (Cmd + Shift + /). I use it navigate the menus by typing in short words.

However, I've just noticed that it's not currently working. Instead, I get an error noise whenever I press cmd+shift+/.



My first thoughts was that either another program is intercepting the shortcut in a global way. But I don't what that program might be.


How can diagnose the cause of this shortcut key failure (Cmd+Shift+/)?
How can I resolve the problem?


UPDATE:


I tried changing the shortcut key in "keyboard shortcuts" to something else (e.g., Cmd + Alt + Shift + /). This alternate keyboard shortcut also triggers the error noise. So this suggests that the problem is not a conflict with another program.
@sameetandpotatoes made some great suggestions. 


I tried a different shortcut key for triggering the help menu and still had the problem.
Restarting OSX resolved the problem.