Using Zen Cart 1.3.8a.

Im using USPS for my shipping method. I have it installed and working properly in my cart. All domestic shipping works like a charm. I have the "First Class International" shipping checked in the shipping module but when I go to 'check out' using an international shipping address it doesn't give me this option. I spoke with USPS and they have the first class international option activated. All other forms of international shipping are working (global express, global priority, etc...)

Is there something else I have to do to have this operate properly?