Hi again,
As Lee advises, in the case of problems, it's
always worth checking the power supply! It
MUST be capable of supplying a minimum of 2 amps at 5 volts and you must use the supplied power lead or an alternative with equivalent heavy duty power wires (minimum 20 AWG), though I would be surprised if this is the issue in your case viz. the Mode C/S select option not appearing on the Configure Screen. I think it is much more likely that the problem is a connectivity issue between the Raspberry Pi and the RF Bridge.
From the screen grabs I take it that you are not in the UK (Norway?). Are you able to try a manual reinstall of the software before returning the unit? This requires a full overwrite reformat of the microSD card with Size Adjustment 'ON' using SD formatter and then downloading and re-installing a fresh copy of the software from
http://pilotaware.lode.co.uk as per the manual software update instructions in pages 44/45 of the PilotAware Operating Manual - available on ...
http://www.pilotaware.com/wp-content/uploads/2017/07/170619-Operating-Instructions-.pdfSounds complicated, but once you have done it, it becomes straightforward and was until relatively recently the only way we could do updates. I'm not certain it will help, but it would certainly be worth a try if you are happy to give it a go.
Regards
Peter