How to reproduce this issue:
Please elaborate on your query more. The items you select in "For shipment with matching items" may not fit your criteria.
Steps To Reproduce
- Check your coupon code configuration again
- Check the items that you select again
- Check on the shopping site that you added to the cart
- Check the priority of the coupon code if some other coupon code is already applied.
- Debug the shipping methods how you configured it.