This error occurs when SEKO EasyPost cannot create a label because of missing or invalid customer contact details, most commonly a missing or incorrectly formatted phone number.
Error message
"SEKO API returned errors: Failed to create shipment. [EasyPost_Error: The request could not be understood by the server due to malformed syntax.]"
What this means
SEKO EasyPost rejected the request because customer contact details are missing or invalid. This is most commonly a phone number issue — either missing, or with an incorrect number of digits for the country.
How to fix it
Open the RMA.
Review the customer's contact details.
Add a phone number if one is missing.
If a phone number is present, check it has the correct number of digits for the country. For US returns, use a 10-digit phone number.
Regenerate the label.
If the issue continues
Contact support with the RMA ID and a screenshot of the error.