Hello everyone.
I have Cubase 5 and Cubase 9.6 and Tascam US 2020 interface. Windows 10.
I decided to get 8 more channels, so I connected Tascam to out of old Alesis ADAT by lightpipe (toslink
cable).
Tascam and adat are locked (interface receiving clock from adat) , interface is receiving all 8 channels, plays fine. What is more, analog inputs on Tascam are working in the same time perfectly too.

When I what to record digital inputs in Cubase, daw is receiving no sound.

All inputs in 'vst connections' section are connected.
Daw can't get no sound.

What is more, while digital input (lightpipe) is activated, Cubase gets no analog signal too. Analog appears in daw only when adat input of soundcard is switched off (internal clock).
This happens in both Cubases (5 & 9.6).
What Is wrong?

Please, need your advice.

P. S. Almost five years I'm recording on tape recorders like Tascam msr16, sometimes on HDD recorders, and maybe I forgot something.
Need your input!

Maybe some screenshots of software settings (Tascam and Cubase) would help.