This listing error from Walmart is just referring to a missing attribute, but it can be unclear as to which Zentail attribute Walmart is requiring.
Walmart calls its bullet points "Key Features", and and an item cannot be listed to Walmart without them. To fix this error, you'll need to fill out the Bullet Points. They can be found in the Category and Description section of the Edit SKU page, or you can edit them in a QuickEdit view like this one.