Maybe you have stumbled upon the following error message: ⚠️USPS: Customs declaration is required for military shipments via the USPS. (label could not be created & sent to customer)⚠️
Customs declarations are not supported for international prepaid labels at the moment, see also:
In this case a label will not be created. The prepaid label needs to be created manually outside of our platform and sent to the customer directly.