If you are a Sophio FBS supplier and have activated Fedex One Rate in your Shipstation, the screenshot below is how orders will be configured. Notice that the service is a Fedex 2 Day service and that the package is set to a special One Rate Pak, Envelope, or Small Box.
if Shipstation has incorrectly specified Fedex One Rate due to the dimensions being too large or too heavy, please change the service to lowest cost service (usually Fedex Ground). Also be sure to change the packaging to Package.