When some merchants try to create shipping discounts, they receive an error message saying that "Shipping discounts are not enabled on [their] store."
Our shipping discounts are built using Shopify's Shipping Discount Functions API. However, this API is currently only available to stores in the checkout extensibility developer preview: https://shopify.dev/docs/api/functions/reference/shipping-discounts
UPDATE: We have reached out to Shopify for a timeline on when this API will be available on all stores, but there is none yet.
We are hoping that Shipping Discount Functions will be made available for live stores in the upcoming 2024 Winter Editions.