USPS shipping method and free shipping

I have installed the USPS Shipping method woocommerce extension on this client’s site. they are wanting the option to allow free shipping when a customer orders 4 or more bottles. I create a shipping zone for free shipping and require min order amount that I set to the cost for 3 bottles before taxes.

when I test it and add 4 bottles to the cart, the shipping section displays a note about needing a valid address, so I enter the address to my house and then try to check out and it gives me an error saying there isn’t a valid address.

but if I change the quantity to anything below 4 it displays shipping choices and allows you to check out. current I removed the free shipping zone so that customers are able to order since the site has been made live.

Does anyone know what the issue would be?

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