here is my use case:
I create a configurable product with options and variants.
I am able to define a specification of the product.
then, I have an issue when I try to create a variant part. (Action / Request Deliverables). Here is the requested deliverables message:
Go to Solution.
well, I answer myself if someone have the same issue:
it was due to a windchill preference:
Variant Subtype --> set it to --> com.ptc.windchill.option.model.Choice