Leave the service address empty and you land in the test environment
There is a default worth watching in the Sürat Kargo connection: if the service address field is left empty, the test (prova) environment is used rather than production. In many other integrations leaving a field empty means "default to live", so this reversed behaviour surprises people. The consequence: shipments appear to be created without error, but no real carrier record comes into existence.
Going live is straightforward: write the production service address Sürat gave you into this field. When you do want to work against the test environment there is a separate test switch, and ticking it is enough.