Recently I received couple of questions regarding Online search from MSDN Offline Library from the people who were having trouble searching online topics.
Some people were using multiple language version of MSDN Library. Some people were using localized version of MSDN Library on the English OS or the other way around.

If you have internet connection but can't search from MSDN Offline Library please check following settings in the Tool - Option menu before you report a bug.

       Tool - Option
                 Help - General: See if "Online Topic language:" is set to the language you want and see if "Also show English topics" is checked.
                 Help - Online:   See if "Try local only, not online" is selected.
                 International Setting  - See if the language setting is correct.
                 Web Browser: Check the Search page URL. If your online search is not working try search.msdn.microsoft.com

For example somebody who's using French MSDN Library on the English OS and wants to search French topic, check the topic language is set to French.
People who's getting 0 (zero) MSDN online result, make sure "Try local only" is not selected in the Help - Online setting.