Presonus 1824c with Cubase / Nuendo is not working properly

We have 2 Presonus Studio 1824c. The 8 outputs are configured as stereo 1, 2, 3, 4. Also the inputs. (We have several computers with Cubase and Nuendo).
Unfortunately, no one is able to route an audio track to stereo 2, 3 or 4 (Output 3 - 8). Everything comes out only to the first stereo 1 on the device. The Presonus mixer is deactivated.
If I activate the mixer, then Cubase / Nuendo routes all Stereo 1, 2, 3, 4 (which I select in the mixer) to * all * outputs on the device. The same thing comes out on all 4 stereo pairs. It’s like having a device with only one output. The settings of the Presonus Mixer are irrelevant.
I need the separate outputs to insert external effects.

Has anyone got the device working? And if so, how?
Many Thanks.