Check out

I am having trouble with the check out page. When I try to order a product,then when I enter the zip code I get this message Sorry, online ordering is unavailable to this destination and/or weight. Please double check your destination details.
I have signed up with UPS and USPS. I have entered my username and password that I use with UPS and USPS, what I am having trouble with the UPS XML API Key. Where do I find this key? I thought I entered the right number.

Thanks
Robert