Free Shipping Method Doesn't Work with This Plugin

[Moderate]

When enabling this plugin, the free shipping method does not work. We would like to offer free shipping over a certain dollar amount, but cannot when this plugin is enabled. When the plugin is disabled, free shipping over certain dollar amount works fine. Is this a known issue or have we done something wrong?

https://wordpress.org/plugins/printful-shipping-for-woocommerce/

We want to still allow Printful to handle our fulfillment and shipping, but allow for free shipping to be an option when a coupon is applied. Right now, if a customer enters a free shipping coupon, they still have to select a shipping method (generated by Printful), all of which cost money. There is no “free shipping” option even when the coupon is applied. What needs to happen is Printful needs to add a “free shipping” shipping method that costs $0, so that when a coupon is applied, the customer can select that. I would assume that free shipping method would be the cheapest method possible.