Here are some helpful guides to activating Google Analytics Enhanced Ecommerce 

Activate within Google Analytics (Required)
​https://support.google.com/analytics/answer/6032539?hl=en

Shopify
​https://help.shopify.com/en/manual/reports-and-analytics/google-analytics/google-analytics-setup

BigCommerce
​https://support.bigcommerce.com/s/article/Setting-Up-Google-Analytics#recommended

WooCommerce
​https://woocommerce.com/products/woocommerce-google-analytics/
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