Create contracts rest API , BillPlan Error "The action "create" is not enabled."

Summary

I am able to create headers, lines with associated projects to lines. But but not able to create BillPlan details I am getting the below error: "The action "create" is not enabled."

Content

Could you please help with the below error:

I am able to create headers, lines with associated projects to lines.
Now I am trying to create BILLING details I am getting the below error:

Error: The action "create" is not enabled.

Rest Api : /fscmRestApi/resources/11.13.18.05/contracts

1.Payload used for creating the header and line with the associated project( below payload working fine without any issues):


{
"ContractTypeId": 300000013511963,