ESP8266 HTTPClient REST call problem

[Jagdriver]

I have a Sketch where I call a REST service, and it was working fine on my ESP-12E Module. The REST call is to a Raspberry PI 3 running Windows 10 IoT. The Raspberry was connected to the network via WiFi. Then I changed the Raspberry to the Ethernet adapter and disabled the WiFi. After the change it is no longer possible to call the REST service form ESP-12E Module, it sends out an ARP Request, but then nothing happens. I then tried to load the sketch on a SparkFun ESP8266 Thing Dev, and here the Sketch works fine. Is the anyone out there that has semilar experiences?