Woocommerce Custom Logged-in Price not transferring to Checkout

Hi

In a WooCommerce store I want to offer a 20% discount to logged in users for a particular brand.

The following code is successful in displaying the correct pricing on the product and archive templates, however the discounted price is not appearing in the cart or checkout

Any ideas? TIA ????

    // Utility function to change the prices with a multiplier (number)

    function get_price_multiplier() {

      $prod_id    = get_the_ID();
      $terms      = get_the_terms($prod_id,'product_brand');
      $brands     = array();
      $brand      = '';
      $count      = 0;

      if(is_array($terms)) {
        foreach ($terms as $term) {
          $count ++;
          if($count == 1) {
            $brand = $term->slug;
          }
        }
      }

    
      if ( (is_user_logged_in()) && ($brand == 'acme') ) {
        return 0.8; // 20% off
      } else {
        return 1;
      }

    }

    // Simple, grouped and external products
    
    add_filter('woocommerce_product_get_price', 'custom_price', 99, 2 );
    add_filter('woocommerce_product_get_regular_price', 'custom_price', 99, 2 );
    
    // Variations
    
    add_filter('woocommerce_product_variation_get_regular_price', 'custom_price', 99, 2 );
    add_filter('woocommerce_product_variation_get_price', 'custom_price', 99, 2 );
    
    function custom_price( $price, $product ) {
        return (float) $price * get_price_multiplier();
    }
    
    // Variable (price range)
    
    add_filter('woocommerce_variation_prices_price', 'custom_variable_price', 99, 3 );
    add_filter('woocommerce_variation_prices_regular_price', 'custom_variable_price', 99, 3 );
    
    function custom_variable_price( $price, $variation, $product ) {
        
    // Delete product cached price  (if needed)

        wc_delete_product_transients($variation->get_id());

        return (float) $price * get_price_multiplier();
    }
    
    // Handling price caching (see explanations at the end)

    add_filter( 'woocommerce_get_variation_prices_hash', 'add_price_multiplier_to_variation_prices_hash', 99, 3 );
    
    function add_price_multiplier_to_variation_prices_hash( $price_hash, $product, $for_display ) {
        $price_hash[] = get_price_multiplier();
        return $price_hash;
    }