Please make sure, that you have the desired search plugins enabled in your plugin manager. If all the search plugins are disabled, the searh will not work! (like on the picture)

Also, make sure, that you have selected the search areas in the Universal AJAX Live search settings panel. You need to select which plugins do want the Live Search to fetch.

Related Knowledgebase articles:

Universal AJAX Live Search is not working, only a blank error message is shown
Images not showing in Universal AJAX Live Search