Optical cable with my speaker system fading sound

I currently bought an optical cable for my speaker system and it seems it's making my sound fade out, every time my computer is making no noise the panel says "No Digital Data" but as soon as Skype or Telegram or I start music the sound fades in then works with no problems and says "Effect: Stereo" (cause it's put as Stereo). I posted on Logitech support about this too as I'm using a Logitech Z-5500 and see what they say, but I wanted to ask here too if it's maybe a Windows feature with digital cables or optical cables.

Gotten answer from Logitech now and talking to them, no one here knows of it? I can probably post a short video of how it acts if needed.