URGENT HELP 5.1 SURROUND SOUND

Hi guys,

I’m having some difficulties setting up surround sound on Steinberg Nuendo 8. I currently have Sony DH550 speakers running directly to the PC via HDMI (I know this isn’t good practice its a last minute resort). I’ve tested the surround sound and it seems to work fine however my Nuendo 8 only sees the front left and right - it isn’t registering the surround speakers or sub. If anyone has any ideas on how I could get Nuendo to recognise the extra speakers it would be greatly appreciated! thanks!

https://steinberg.help/nuendo/v8/en/Nuendo_8_Operation_Manual_en.pdf#page651