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ShipStation provides a setup checklist on their end:
ShipStation Shipping method service Mapping
You'll also need to make sure that you have mapped your Shipping Methods between the two systems:
https://help.shipstation.com/hc/en-us/articles/360025870232-Service-Mapping
https://help.shipstation.com/hc/en-us/articles/360036323651-Use-Shipping-Presets
API integration
Integration uses the Web Service transmission mechanism option in the Transmission mechanism list of the Distribution Center editor .
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