You probably have some app connected to sync Shopify customers to your list. If you use an app like “MailChimp for Shopify” to sync new customers, that accepts marketing emails, to your MailChimp list Coupon Carrier won’t be able to detect them when they are added.
The reason why is that MailChimp has a bug in their API that causes it not to notify Coupon Carrier when a subscriber is added via their app “MailChimp for Shopify”. That app also takes a few minutes before it syncs new customers to your MailChimp list.
If you select a MailChimp list that is connected to your Shopify store we can detect it and show you a warning and how to fix this issue:
The guide linked to in the warning message describes how you can add a custom notification webhook in your Shopify store that Coupon Carrier uses to detect new customers and instantly add them to your MailChimp list. This also makes sure that Coupon Carrier can detect them and distribute the code.