Assignment of Cost Component Structure

Dear Experts,

I feeling very strange to say this:

I had created Cost Component Structure. It has assigned automatically to PPC1 Costing Variant in OKKN. Because In OKTZ Assignment done at level of all company codes, Plants and Costing Variant Fields by masked with ++++.

This is standard behavior. But when I tried to assign my new CC Struc to new costing variant,

System getting this error message: "choose costing variant not for std cost est or mask costing variant."

Please help me

Regards,

Balaji Rao Bhonsle