OR doesn't show results when all options set to ALL

No, it should return all results.
Can you give me the url?

https://diviplay.wptraining24.com/ultimate-search/

But it is a big mess there, beware ??
Just click on search when the site opens, and you will see no posts.

The setting is:
Taxonomy Fields
Boolean relationship between the taxonomy queries : OR

ermm…I can see the query was correctly sent but nothing returned.
It is different with ‘nothing found’. Something wrong with the server side.
Did you tried ‘AND’ relationship?
Or you can remove of the filter to see if it is working.

I doubt that your server can’t handle the ‘OR’ queries, because it is a lot more resources consuming when using ‘OR’. It is best to avoid using it.

You can try this method to debug:
Add following codes to your theme’s functions.php.

add_filter('uwpqsf_result_tempt', 'customize_output', '', 4);
function customize_output($results , $arg, $id, $getdata ){
	 // The Query
            $apiclass = new uwpqsfprocess();
             $query = new WP_Query( $arg );
             print_r($query);
		ob_start();	$result = '';
			// The Loop

		if ( $query->have_posts() ) {
			while ( $query->have_posts() ) {
				$query->the_post();global $post;
                                echo  '<li>'.get_permalink().'</li>';
			}
                        echo  $apiclass->ajax_pagination($arg['paged'],$query->max_num_pages, 4, $id, $getdata);
		 } else {
					 echo  'no post found';
				}
				/* Restore original Post Data */
				wp_reset_postdata();

		$results = ob_get_clean();
			return $results;
}

This will show the query objects in the results div. It will give me more info on wrong with the searches.

I tried AND and it does return a blank page as well.
I couldn’t find a way to reset the setting, so once AND or OR is set, there is no way to deselect, or how can I do it?
I integrated the code, maybe you can find out more, it is now set to AND.

I would like to achieve that it starts with a list of all posts, and then when people choose a filter it gets filtered. I guess if I manually add a postlist generating shortcode into the DIV, it will be replaced by your plugin with the filtered list once people press “Search”, right?

I tested the search, and I still can’t get the info because it is not output anything when search for all. Did you turn off the debug mode (in the wp-config.php file)? If so, try to turn it on.

I would like to achieve that it starts with a list of all posts, and then when people choose a filter it gets filtered. I guess if I manually add a postlist generating shortcode into the DIV, it will be replaced by your plugin with the filtered list once people press “Search”, right?

Yes

The debug is now set to true. Thanks for all the help…

ermm..seem no errors found. Can you try to switch to default theme and try again?