WordPress Custom Post Type not showing in Search Results
Add this code in search form. set custom post type in hidden field value.
<input type="hidden" name="post_type" value="post type name" />multiple custom post type in search form
<input type="hidden" name="post_type" value="posttype1, posttype2, posttype3" />
To search for multiple custom post type, you could also duplicate the input in your search form
<input type="hidden" name="post_type" value="post_type1" /><input type="hidden" name="post_type" value="post_type2" /><input type="hidden" name="post_type" value="post_type3" />Tested on WordPress 5.3