When open parts from older NX versions get the message:
"The Material Attribute was reset because it did not match the material assignment. This action was taken based on your Customer Default setting."
After that the material is removed.
The immediate message when opening a part file: "The Material Attribute was reset because it did not match the material assignment. This action was taken based on your Customer Default setting.", is indicating that there is an attribute setting which doesn't match the actual assignment. What was found is that a material is assigned to a "condemned / sleeping body". In older version such as NX12, these assignments were considered valid for the material attribute, but due to confusion related to mass calculation and other downstream usages, these assignments are no longer considered for the material attribute (only bodies that can actually be selected are considered for the attribute setting).