When processing, you might come across the "120076 - Missing or invalid USPS Endorsement" error.
When using UPS Mail Innovation services it is required to define the USPS Endorsement, for USPS know, once the shipments are under their responsibility, how to handle the address and what to do if the packages are undeliverable.
Feel free to follow this video guide, or the step-by-step procedure below.
To do so, you will have to:
1. Access Clients under the Maintenance dropdown
2. Select the Client related to the case
3. Edit the billing account related to the case
4. Select the Carrier Options tab
5. Select the USPS Service Endorsement from the dropdown according to what's applicable to your operation
6. Press Save to commit the changes