To correct the below error message you need to add these missing attributes.
You can add these attributes under Inventory-> Product attributes-> New attribute
For the above error message you need to add the attributes "age_range_description" as follows.
(If you do not have a default value simply enter n/a)
Once you have created this attribute, please edit the product you are trying to list and select the 'attributes tab'
From here you can select the new attributes you have created and enable them on this product.
Once you have added the attributes to the product please select the listings tab and select 'update listing'
You will need to send a full update to Amazon and this will push across the new attributes for you and send your listing through.
If you still receive the same error message after adding these attributes please contact our support team at firstname.lastname@example.org