In order to qualify for any promotional offers involving free shipping, your purchase needs to meet our $95 / $175 / $150 minimum order amount (for USA /Canadian / International orders respectively) after all discounts have been applied.
Here's an example:
You add $100 worth of items to your cart and use a fabulous coupon that provides you with a 20% discount! Your new total before taxes and shipping would be $80.00.
Since that price is below our normal minimum order amount, you wouldn't be able to choose free shipping as an option. Add an item or two to your order that will bring the price after discounts to $95 or more, and then you'll be able to take advantage of that shipping method!