How To Hide shipping methods for specific shipping classes in WooCommerce

To use multiple shipping classes, you should first defined them in an array and in the IF statement you will use in_array() conditional function this way:

add_filter( 'woocommerce_package_rates', 'hide_shipping_method_based_on_shipping_class', 10, 2 );
function hide_shipping_method_based_on_shipping_class( $rates, $package )
{
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    // HERE define your shipping classes to find
    $classes = [3031, 3032];

    // HERE define the shipping methods you want to hide
    $method_key_ids = array('flat_rate:189');

    // Checking in cart items
    foreach( $package['contents'] as $item ) {
        // If we find one of the shipping classes
        if( in_array( $item['data']->get_shipping_class_id(), $classes ) ){
            foreach( $method_key_ids as $method_key_id ){
                unset($rates[$method_key_id]); // Remove the targeted methods
            }
            break; // Stop the loop
        }
    }
    return $rates;
}

Code goes in functions.php file of your active child theme (or active theme). Tested and works.