No sound via S/PDIF

Hello!

I’ve been using my Vero with sound and video over HDMI to my TV (and then via the 3.5mm headphone jack to my amp). Yesterday I decided that a better sound experience was needed.

Now, my amp (http://nadelectronics.com/products/hifi-amplifiers/C-316BEE-Stereo-Integrated-Amplifier) does not allow other connections than RCA so I got a DAC (https://www.hifisound.de/en/Hifi-Components/Multimedia-Components/DA-Converter/ARGON-MINI-DAC-D-A-CONVERTER.html).

I’m connecting my Vero with an optical cable to the DAC then via RCA to my amplifier but it’s dead silent. No movies seem to generate any sound, neither does playing stuff over airplay. There is red light coming from the optical cable when I pull it out of the DAC. Everything is switched to S/PDIF output on the Vero, I have the right RCA-plugs and everything is switched on. And I have tried to change every other setting possible in audio settings without success.

Now, I have no idea what to do. Anybody?

Thanks in advance.