Are you saying Joomla search results are empty or are you searching your userlist and it displays nothing? Those are two completely different usages. For Joomla search to work on CB users you need to have CB Search Bot installed and it does not work with Joomlas smart search module. For CB search you need to have a menu item to your userlist where you can begin searching users.

What do you mean by its empty? It specifically says there were no results or the rows where users should be display nothing? If the rows are empty it's a permission issue for your fields and/or the tabs the fields are on. Ensure CB Core is Public within CB > Plugin Management. Next check the tabs of the fields you have on your userlist and also set them to Public. If still nothing then edit your userlist and make sure your filters are correct as it sounds like you maybe filtering out your users. Beyond that I've no idea and recommend reviewing the CB Primer Book carefully regarding userlists as something was not configured correctly.