The error message (Error: Error Occurred: Status: Toolkit.ExternalAPI.Couriers.GFS.WebService.V5.ResponseDetails StatusCode0030 StatusDescription: Contract No is not registered for carrier StatusMessage: Invalid request structure) from GFS occurs due to the wrong Contract Number being mapped to a Carrier. To check this, follow these steps:
Click Connect, then Courier Integrations.
Click GFS and find the affected connection.
Click Manage Contract No Mappings.
Ensure there are no spaces before or after the ContractNo and that the correct number is used for the required carrier.