New Styles Not Rendering On Mobile Phone and Tablet

Can you see the changes in an incognito window on mobile? If so, then its most likely a mobile cache issue and a common way to fix that is by adding a version number to your css file i.e.

wp_enqueue_style( 'my-main-styles', get_stylesheet_directory_uri() . '/style' . $suffix . '.css', array(), $version_number_here );

If breaking the cache that way doesn’t work I would try refactoring some of your code so it’s mobile first as @WebElaine said and troubleshoot from there if it looks like there’s an issue with your media queries.