No audio signal on the Hifiberry via Volumio

Hello Volumio - Congregation,
I have the following problem. To equip my Rasberry Pi with Volumio, I bought an Hfiberry DAC + RCA module from Hifiberry to connect the music player to my stereo system via Cinich. I plugged in the module and made the settings in Volumio. There is no audio signal at the cinich sockets and the following error messages appear when listening to music from the server or internet radio.

What am i doing wrong?

MfG Jörg