If you encounter an error message stating “Missing Dimensions” while creating an FBA shipment, it indicates that the listing in question lacks item dimensions or package dimensions in your Seller Central account.

To address this issue, you should proceed by updating the product dimensions on your Amazon Seller Central account for all the listings mentioned in the error message.

Please note that it may take up to an hour for the updated dimensions to be reflected on these products. Once the dimensions are updated, you should be able to proceed with the shipment as intended.