Precondition failed with Http Code 412 in SAP Getway Client

Hello Experts,

I am testing the POSTGoodsReceipt service. The service url is as below.

/sap/opu/odata/sap/API_INBOUND_DELIVERY_SRV;v=2/PostGoodsReceipt?DeliveryDocument='180001331'

First I get the etag from the response.

Then set the etag in the http request header. But I still get the 412 error. Could you give some suggestions?

Thanks,

Jerry