I have setup a shopping cart on a client site, http://videoplayground.net, Requested and received API username for USPS and entered it into the settings. Client sells services like converting VHS tapes to DVD. I added all the products and variations as physical products and not services so the plugin will calculate shipping and add it to the total. The shipping is prepay return shipping of my client's customers' original media. I added weight of everything, like the weight of a VHS tape to the product of Convert VHS to DVD. When I went to test everything, at #3 of the checkout process, Shipping Method, it says "There are no shipping services available for this type of package in your location." USPS is listed there, but it cannot be selected. I noticed when entering my shipping info as a customer, zip code text above input is replaced with 60655, client's base zip code, but, I was able to enter my zip code as the ship to zip.