Set your TV to these settings:

eARC: Auto

Digital Audio Out: Auto 1

Dolby Digital Plus Output: Dolby Digital Plus

Pass Through Mode: Auto

yes. thanks. I already saw this answer in other posts, but like most people, it doesn't work either. it seems to be more of a hardware problem than a configuration problem. I already asked SONY too...

UPDATE

SONY's response:
-Please disconnect the sound system and test the CD with the Blu-ray player via the TV speakers only and let us know the result.

my answer:
I disconnected the sound system from the TV and now you can hear the sound through the TV speakers. Is it possible that there is a problem with the HDMI eARC connection?

lets see what they say…

I'm still looking for a solution. maybe buy some extra hardware and connect the SONOS Arc in another way? 

If you set the DSD Output Mode setting on the X800M2 to OFF, do you get any audio when playing an SACD?

hello again. thanks for the advice, but unfortunately it still does not work. still no sound. 

UPDATE

SONY's response:
* Please disconnect the TV from the power supply for approx. 5-10 minutes and restart it.
* Press and hold the On/Off button on the remote control until the TV shuts down and starts up again automatically (soft reset).
* …

and you know, practically check/update the firmware version of the TV and reset the settings to factory mode. naturally, it didn't work. no audio.

I wanted to try a couple of things. I got a Sonos Optical Audio Adapter, connected the Arc to the adapter and the adapter to the Optical Audio Port on the TV, just to make sure the eARC port isn't blocking something. it didn't work. no audio. if i watch a movie on netflix, audio comes out, of course not in Dolby Atmos format, but you can hear it.

The second thing I tried was to use the HMDI 2 port of the UBP-X800M2, connecting it also to the Optical Audio Port of the TV, this time I could not listen to any audio, neither from CDs nor from SACDs.

it slowly becomes a bit frustrating...