It seems the latest WooCommerce is forcing a CSS override on the cart.
Here is our demo:
If I remove the WooCommerce small screen CSS, yours then looks like so:
Please install and activate the supplied child theme, inside the child theme functions.php
file please paste this:
// Remove each style one by one
add_filter( 'woocommerce_enqueue_styles', 'jk_dequeue_styles' );
function jk_dequeue_styles( $enqueue_styles ) {
unset( $enqueue_styles['woocommerce-smallscreen'] ); // Remove the smallscreen optimisation
return $enqueue_styles;
}