Roon and Lynx AES16e

I am about to use my newly purchased Acourate correction program.

As a part of the project, I bought a Lynx AES16e sound card, which will feed my 3 x Lyngdorf TDAI2200 with digital signals.
So far, I managed to install the card, which is connected to my NUC via Thunderbolt 3.
I can make test tone work, directly from my PC, but when I use Roon, I run into problems.

Roon displays the Lynx in the Audio folder, and all individual channels, but the “PLAY” botton is faded out; I cannot start playing music.
Roon runs perfect, via my Topping D10s.

When this problem is (hopefully) fixed, I will move on to working with Acourate.

Any idea, what causes the problems?