Promo codes can be used to advertise special offers and drive revenues in your store. When you install ShopSync, we'll pull any discount codes you have created.
Promo codes are not synced in real-time from Shopify to Mailchimp. Typically, these populate every few hours. However, if you're not seeing them right away, you can click the "Refresh" button on the app page that will fetch the latest codes available in your store.