Error 8801

The child SKU '${child_sku}' could not be added to parent SKU '${parent_sku}' because child SKU '${other_child_sku}' has the same variation attributes ${attributes} and is already associated with the parent SKU.

Two of your child SKUs have the same variation attributes, so one must be deleted. Please review your list of SKUs and make sure that there are no duplicates before uploading again.