Error using API discovery:device. No response from discovery service: Connection refused.

[#1]

I'm trying to call the API to get detail about devices discovered by Infoblox. In this case, I currenlty have one node and I call this API:

https://10.150.0.50/wapi/v2.7/discovery:device?address=192.168.140.129&_return_fields=name,description,os_version,

The API gave me this error, Can you help me to understand the reason?

{ "Error": "AdmConDataError: None (IBDataError: IB.Data:No response from discovery service: Connection refused.)", 
  "code": "Client.Ibap.Data", 
  "text": "No response from discovery service: Connection refused."
}

Thank you,