Also Tele2 make sure you don’t have a VCR or any other device connected to the TV that is on and sending out a scart control signal (simplest way to check is to put all other things into standby).
If a VCR is sending out a scart control (for example if the VCR has a ‘TV/VCR’ button on it and it is set to VCR) the digibox will override the VCR in terms of what is displayed on the TV but the control signal from the VCR will be passed onto the TV and it will then only accept composite inputs. (Not sure if that is the case for all TVs, but it seems to be for many).
This happens to my folks all the time, meaning they hardly ever watch things in RGB, but then again they don’t seem to see the difference in picture when I show them what’s it’s like with the video set correctly