Google Tag Manager - No tags in container

So I tried to implement google tag manager as follows : https://developers.google.com/tag-manager/enhanced-ecommerce . But nothing happened to me.

Nothing is posted and nothing is shown in the tag manager admin. Here is a simple code snippet taken from the tutorial:

dataLayer.push({
        'event': 'addToCart',
        'ecommerce': {
          'currencyCode': 'EUR',
          'add': {                                // 'add' actionFieldObject measures.
            'products': [{                        //  adding a product to a shopping cart.
              'name': 'Triblend Android T-Shirt',
              'id': '12345',
              'price': '15.25',
              'brand': 'Google',
              'category': 'Apparel',
              'variant': 'Gray',
              'quantity': 1
             }]
          }
        }
      });

I've installed Tag Assistant and it says Tag Manager is loaded with the correct container ID. Any ideas why nothing is posted and the tag manager admin console is empty?

nk！