I tried and tried with my serial gateway, and never got it to function porperly. The serial port was working I could see it and data, but OH3 just refused to recognise the data. After a week, I decided to abandon the serial and flashed a esp8266 attached the nRF to it and bobs my uncle as we say. It goes via MQTT, so takes a little more settting up but works fine. If you want more info I will dig out the pages I used to make it work.