My Humax DTRT 2120 box does not give surround sound via the Netflix app. Amazon Prime app does give surround sound. Both apps running on Sony smart tv do give surround sound. Youview box is connected directly to AV receiver by HDMI. Sound is set to surround.
Fixed! Go to the fix.
As far as my investigations have found (and they may be wrong, please do let me know if you think that's the case) the Netflix app on our YouView service is built to not currently offer surround sound, I'm afraid.
It appears it's only available via a YouView UHD service via the HDMI output with Sound to Surround in the Picture & Sound settings menu to get 5.1 via the HDMI output. Unfortunately we don't currently offer YouView UHD which is why it doesn't appear to be working for yourself - As far as I can tell only the DTR-T4000 Ultra HD box offers Netflix 5.1 Surround sound services.
Re: No Netflix surround sound
To be clear from what I've read about the matter it's a restriction put in place by Netflix's app on some set-top boxes. When the app came out in 2014 YouView did a community post about the feature here, and while that's 5 years old now by the sounds of the BT Community Forums it's been a constant battle to get Netflix to enable it on YouView's set-top boxes only allowing it on the UHD box which I believe was only released at the beginning of the year.