This issue may happen in two cases:
The product you analyze has never been in Amazon warehouses. Amazon does not have data on the product size and weight – in that case, Amazon cannot calculate fees.
Your Amazon Seller account is fresh and not configured. Agree to Amazon FBA terms. Go to the Fulfillment by Amazon on the "Gear" menu or follow the link: https://sellercentral.amazon.com/fba/register/status
The FBA fees data will be displayed after 15 minutes.