update your permalink structure to something other than the default for landing pages to work.", admin_url( 'options-permalink.php' ) ); } else { if ( $permalink_structure === '/%postname%/' ) { $root_sluggable = true; } else { $root_sluggable = false; if ( $slug_type == 0 ) { $root_error = true; $error_messages[] = "Invalid landing pages link structure."; } } if ( $slug_type == 1 ) { if ( empty( $slug ) ) { $folder_error = true; $error_messages[] = 'Landing pages folder name is required.'; } else if ( preg_match( '/[^a-zA-Z0-9-]/', $slug ) ) { $folder_error = true; $error_messages[] = 'Landing pages folder name is invalid.'; } } } ?>
Landing pages link structure:

", $error_messages ); ?>

style="color: red;"> checked disabled="disabled" value="0" class="landing-pages-slug-type"> Site Root Site Root /sample-landing-page/ (available only with Post name permalink structure)
style="color: red;"> checked disabled="disabled" value="1" class="landing-pages-slug-type"> In Folder / disabled="disabled" value="" class="regular-text code" style="width: 175px;" />/sample-landing-page/