Application server is sending RST,ACK packet when API is called from IBM Data Power appliance

Hi, We are working on version 8.1.3 and we are able to call the REST API from Postman but when we are trying to call it from IBM Data Power appliance, application server is sending RST,ACK packet in response. We do not see any hit from this appliance in Appserver or IIS logs. What could be the reason for RST, ACK packet?