The error comes directly from Amazon.
This probably means that something is wrong in the SKU settings in Amazon Seller Central, or you have stored a best before date that is in the past. If no best before date is required, then the delivery schedule may have been created anyway!
Due to the error, Amazon is not accepting the box information and that is why the dimensions are still missing in Seller Central.
A quick fix would be to simply enter a date that is far in the future.
A real solution would be to check the SKU settings and/or contact Seller Service to correct the SKU settings.