What would happen if the dimensions for a particular SKU is not present at Amazon Portal?

Assure pulls the dimensions from  amazon portal and sends to the amazon back-end. If dimensions are not present at portal, inventory will be updated without dimensions at Amazon Back-end against which Amazon can take the order from customer, but not able to push the same to Assure.

Error '401 Access denied' while using Amazon MWS scratch pad?

This happend because the Seller is either disabled or the Auth token got expired. The authtoken expires after 1 year