[Wordpress] Add profit to datalayer (gtm4wp)

fucntions.php

/**
 * Requires Plugin: Google Tag Manager for Wordpress & WooCommerce Cost of Goods
 * Author: Mattias Ghodsian
 * Donate a cup of coffee: https://www.buymeacoffee.com/mattiasghodsian
 * Donate Eth: 0xBBB96204E45D11C9799c6B12E6eE6F0d4A071Ef5
 */
function gtm4wp_add_profit_datalayer_data( $dataLayer ){
	if ( is_order_received_page() ){
	    $orderID    = $dataLayer['ecommerce']['purchase']['actionField']['id'];
	    $orderItems = $dataLayer['ecommerce']['purchase']['products'];
	    if ( $orderID && $orderItems ) {
	        $total_price = 0;
	        foreach ($orderItems as $key => $item) {
	            $productID  = get_product_by_sku( $item['sku'] );
	            if ( $productID !== false) {
	                $buyPrice = get_post_meta( $productID, '_wc_cog_cost', true);
	                if ( $buyPrice ) {
	                    $total_price = $total_price + ($buyPrice * $item['quantity']);
	                }
	            }
	        }
	        // $dataLayer["ecomm_profit"] = ( $dataLayer['ecomm_totalvalue'] - $total_price );
	        $dataLayer["ecomm_profit"] = ( $dataLayer['ecommerce']['purchase']['actionField']['revenue'] - $total_price );
	    }
    }
    return $dataLayer;
}

add_filter( 'gtm4wp_compile_datalayer', 'gtm4wp_add_profit_datalayer_data' , 20);

/**
 * Get product by SKU
 **/
function get_product_by_sku( $sku ) {
    global $wpdb;
    $product_id = $wpdb->get_var( $wpdb->prepare( "SELECT post_id FROM $wpdb->postmeta WHERE meta_key='_sku' AND meta_value='%s' LIMIT 1", $sku ) );
    if ( $product_id ) {
        return $product_id;
    }
    return false;
}

Hi Mattias,

Sorry for my late reply.
I have set up a fresh install of:

WordPress 5.7.1
Woocommerce 5.2.2
GTM4WP 1.12.2

I am still getting the same error, $dataLayer is empty.
Screenshot: https://www.screencast.com/t/dxUxj0loNC