"generate_post_on" - Date Modified Not Showing on Mobile

I'm trying to use date modified for my post date. It shows up fine on my desktop but does not show up when viewing on a mobile device or in mobile view of GeneratePress. Any help would be appreciated.

I'm using the following PHP snippet:

if ( ! function_exists( 'generate_posted_on' ) ) :
/**
 * Prints HTML with meta information for the current post-date/time and author.
 */
function generate_posted_on() 
{	
	$date = apply_filters( 'generate_post_date', true );
	$author = apply_filters( 'generate_post_author', true );
	//if ( get_the_time( 'U' ) !== get_the_modified_time( 'U' ) ) 
		$time_string .= '<time class="updated" datetime="%3$s" itemprop="dateModified">%4$s</time>';
	$time_string = sprintf( $time_string,
		esc_attr( get_the_date( 'c' ) ),
		esc_html( get_the_date() ),
		esc_attr( get_the_modified_date( 'c' ) ),
		esc_html( get_the_modified_date() )
	);
	
	// If our date is enabled, show it
	if ( $date ) :
		printf( '<span style="float: left; margin-right: 3px;">Updated:</span><span class="posted-on">%1$s</span>',
			sprintf( '<a href="%1$s" title="%2$s" rel="bookmark">%3$s</a>',
				esc_url( get_permalink() ),
				esc_attr( get_the_time() ),
				$time_string
			)
		);
	endif;
	
	// If our author is enabled, show it
	if ( $author ) :
		printf( ' <span class="byline">%1$s</span>',
			sprintf( '<span class="author vcard" itemtype="http://schema.org/Person" itemscope="itemscope" itemprop="author">%1$s <a class="url fn n" href="%2$s" title="%3$s" rel="author" itemprop="url"><span class="author-name" itemprop="name">%4$s</span></a></span>',
				__( 'by','generatepress'),
				esc_url( get_author_posts_url( get_the_author_meta( 'ID' ) ) ),
				esc_attr( sprintf( __( 'View all posts by %s', 'generatepress' ), get_the_author() ) ),
				esc_html( get_the_author() )
			)
		);
	endif;
	
}
endif;

I'm using the following CSS:

.posted-on .updated {
 display: block;
 float:left; 
 margin-right: 3px;
}