This error occurs when you do not provide enough product data to properly create a variation (parent/child) relationship between products. To create a variation (parent/child) relationship, you must provide a Variation Theme value for both the parent and the child product. For each child product, you must also provide the variation data that corresponds to the Variation Theme that you indicated.
The most common causes for Error 8016 are:
The product data provided was insufficient for creating a variation (parent/child) relationship for SKU: [SKU]. Ensure that the parent and child share the same Variation Theme and that there is a submission for variation theme attributes (for example, size and colour for Size Colour Variation Theme).
To resolve this error using an inventory file, enter the data in the columns that correspond to your Variation Theme and ensure that the Parent and Child SKUs within the same variation family have the same Variation Theme.
For more information about creating parent/child relationships, visit: Creating Parent/Child Variation Relationships.