I’m replying to an old thread but the steps listed here sorted my no 5.1 sound issue -Thank you.
I have posted my own “solved” thread whereby I managed to get 5.1 working using various steps, however, my success was short lived when mysystem dropped back to stereo for no apparent reason.
Watching films late at night prompted me to set “night mode” using the * button and as JamesM has identified, this subsequently screws up the output of 5.1 Dolby.
Serious bug in the system.
Many Thanks to JamesM for identifying this.