CSS code work at elements test but doesn't work at Child theme

Hello,

I tested the follow codes at chrome elements and it is work. But why doesn’t work in child theme? The child theme is currently working fine with other codes:

.main {
float: left;
width: 100%;
min-height: 500px !important;
padding:0 0 75px
}

(I’m talking about min-height: 500px !important;)

I have function.php file as follows:

<?php
add_action( 'wp_enqueue_scripts', 'theme_enqueue_styles', PHP_INT_MAX );
function theme_enqueue_styles() {
    wp_enqueue_style( 'parent-style', get_template_directory_uri() . 'BookYourTravel/css/style.css' );
    wp_enqueue_style( 'child-style', get_stylesheet_directory_uri() . '/styles/child-style.css', array( 'parent-style' ) );
}

I consulted the theme developer but they can’t fix it. So I want to get help from here. Please help and advise what’s wrong.

Thanks in advance!