Navigating Google search results using keyboard shortcuts
Finally I manage to figure it out!!! if you are using google search settings in Hebrew this awesome feature is not available, so I changed the search settings to english and it works great!
https://www.google.com/preferences
small update thanks @Sanook it looks like the instant results also need to be enabled, I checked it several times and seems that lang should be defined as English and instant results need to be enabled.
2017-07-31 update
It looks like now google abandoned the instant results feature which is causing the whole search navigation via keyboard to be unsupported. I posted in their forum and hope it will comeback sometime... search-forum
As of 2017-07-31, Google removed this feature entirely from search.
I created the open source Web Search Navigator extension to fix this and add extra features (like configurable keyboard shortcuts).
See installation instructions.
Hope you find it useful, but in any case - feedback is welcome!