Volumio with Soekris DAM1021 no sound over I2S

Hello everyone, I have installed the current version of Volumio on my Raspberry Pi 4, the connection to the Soekris DAC is made via the I2S interface ... unfortunately nothing arrives at the Soekris, even the green LED only flashes. To check, I installed moOde Audio on another SD card, what can I say, everything works, the green LED is lit continuously and music comes out ... which means that the connections are correct. Unfortunately, in my opinion, moOde Audio has a somewhat confusing operation, so I like Volumio better!


Here is my config.txt from Volumio:

nitramfs volumio.initrd
gpu_mem=32
max_usb_current=1
dtparam=audio=on
audio_pwm_mode=2
dtparam=i2c_arm=on
disable_splash=1
hdmi_force_hotplug=1

include userconfig.txt
#### Volumio i2s setting below: do not alter ####
dtoverlay=hifiberry-dac
------config.txt. Ende---------------

Many greetings Uwe