Error: The specified HTTP method is not allowed for the resource identified by the Data Service Request URI

Hi Friends:

I have built below Odata Service(Screen Shots) and getting below Error when do POST HTTP Method with URI: /sap/opu/odata/sap/ZXXXXXXXXX_F4M_SERVICES_SRV/FormSet(Matid='100000000000000000',FormTempid='100000000000000001')

But When I execute the same service with out selection parameters: I get Status Code = 201. Please find below snap shot:

URI: /sap/opu/odata/sap/ZXXXXXXXXX_F4M_SERVICES_SRV/FormSet

I am not sure what I am missing here. I googled so much and could not get any help.

My Odata Service:

Appreciate your help in advance.

Kind Regards,

Madhu M V