Yes I have all the carrier services checked. I'll debug because if there are no services offered in Argentina you would expect a friendly message to say that instead of what I'm getting.
Thanks for all your help!
It's still best that you test with the production URL. Your customer should not have to jump through hoops to get an account set up. He just needs to tell FedEx support that he's using nopCommerce that already has a verified plugin to their API and he wants a production account.