How to fix a shipping fees or carrier problem?

First check where shipping costs are managed: in Merchant Center or in the feed when module-managed shipping is enabled. Advertised costs must match those available to a buyer for the product and destination.

1. In PrestaShop, check the active carrier, zones, weight or price ranges, and group, shop and product restrictions.
2. Under Taxes and shipping fees, check the carrier selected for the feed country's zone and any free-shipping rules.
3. Check product-specific carriers as well as the general carrier.
4. Generate the XML and compare shipping with a cart containing that product, using the same destination and currency.

The integration uses the PrestaShop shipping data supported by the module. A third-party shipping module may calculate rates differently: do not assume its logic will be reproduced in the feed. When appropriate, configure a suitable Merchant Center rule and compare it with actual checkout costs.

For detailed requirements: Official Google documentation.