We use an app to control shipping and they rely on the Carrier Services API.
We offer Free Shipping on orders over $100 after discounts.
The problem that we are facing is the the Carrier Services API does not feed over the discount or the total after discounts, so customer are getting 20% off and Free Shipping.
What is the solution to feed over the correct piece of information to recalculate if the customer uses a coupon and is no longer eligible for free shipping?
This is a known feature of custom carrier services. I asked for this to be changed about 5 years ago, or maybe it was 6? Anyway, I keep asking. Maybe one day the payload will be more decorated with things like the discounts applied. But I would not hold your breath. I am hoping we get a more robust option in the near future, as this is truly one aspect of Shopify that has been languishing for a good many years. Till then, you're screwed?