If you're sending shipments to the API, you may receive the following response:
[success] => 1
There won't be an error message accompanying this, but you may also notice that the shipment itself hasn't come into Shiptheory. The reason for this, is usually because the order you're attempting to send, shares the same reference 1 field as a shipment that has already come into Shiptheory before. Shiptheory requires your reference 1 to be unique, as explained in our API documentation: https://helm.shiptheory.com/developer/index.html#book
If you extend your date range to search on Shiptheory, and then search, you'll likely find the same reference having been sent through in the past:
The reason for this, is that Shiptheory sees the reference 1 as already in our system, therefore believes that the shipment has already come through to us, and won't accept any orders sharing. To resolve this, you'll need to ensure all shipments you send through have a unique reference 1 field.
If you have any questions from here, or have further issues after that, please feel free to contact support.