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The plugin is possibly redirecting to a theme search results page that does not exist in your theme. Therefore the search results are not show.
For example in the Twenty Seventeen theme the files needed to display the search box and search results are
searchform.php. Both files can be found here
I suggest you install the default Twenty Seventeen theme into your WordPress installation and then install and run the plugin. The plugin should then have both pages/files to display the search box and the search results, hopefully enhanced the way you want it to be.
If you cannot change your theme then go into your theme files, they are here
wp-content\themes\NAME_OF_THE_THEME\ and look for PHP files that could have to do with displaying the search box and the search results. Looks for files that might have the word "search" in their filename. If such files do not exist you current theme might not support search functionality.
In that case please have a look at https://codex.wordpress.org/Creating_a_Search_Page and learn what you need to build a search page for the website you are working on. Also have a look at this short tutorial on how to make a search form and how to control the relevant search results on your website.
If this does not help let's hear about it. If this answer helped you or solved the issue please mark it as accepted, thank you.