Ensure the Dolby Digital Plus audio-out over the Arc/eARC port is set to Multichannel (bypass)…

Copied/pasted from the user manual:

Home) > Settings > All settings > Sound > Advanced > Digital out format Set the audio out signal of the TV to fit the sound capabilities of the connected Home Theatre System.
• Stereo (uncompressed): If your audio playback devices have no multichannel sound processing, select to only output stereo content to your audio playback devices.

• Multichannel: Select to output multichannel audio content (compressed multichannel sound signal) or stereo audio content to your audio playback devices.

• Multichannel (bypass): Select to send original bitstream from HDMI ARC to the connected HDMI Sound System.

Also for Netflix, be sure to use the English, or original, language track. Also log into your Netflix account via a web browser and check the playback settings under your profile are set to HIGH.

Note:  YouTube “Atmos” videos are stereo PCM, like all YouTube content, anything uploaded is downgraded to stereo.  You need to play actual Atmos content.  

https://help.netflix.com/en/node/23880

Sorry what I meant was, I had tried looking at set up guides etc 

So after some playing around, when using Netflix thought the tv it works, but when using Netflix though the sky app, it doesn’t! 
 

cheers for the help - appreciated :)