Hello.
It would also be helpful to know which version of AbanteCart you are using. The USPS extension may be unable to return estimated shipping costs due to an issue with your account or connection to the USPS API. Here are a few possible causes and suggestions to resolve the issue:
1. Authorization Issue: Double-check your USPS account credentials. Check the AbanteCart error log for any USPS specific messages.
2. verify that the customer’s shipping address is complete and valid.
3. ensure that the total weight of the products in the cart falls within the USPS shipping range. Excessively heavy or oversized packages not supported.
4. To prevent checkout issues, consider installing additional shipping methods like weight-based or price-based shipping as a fallback option.