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 VariationTheme value for both the parent and the child product. For each child product, you must also provide the variation data that corresponds to the VariationTheme 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 VariationTheme and that there is a submission for variation theme attributes (for example, size and color for SizeColor VariationTheme).
To resolve this error using an inventory file, enter the data in the columns that correspond to your VariationTheme and ensure that the Parent and Child SKUs within the same variation family have the same VariationTheme.
For more information about creating parent/child relationships, visit: Creating Parent/Child Variation Relationships.