Fibaro Double Smart Module Switches

Hi all,

I recently bought myself a Fibaro Double Smart Module in order to be able to switch my home ventilation mode (low, medium, high air flow) using Homey. The device manual: Smart Module | Double Smart Module | FIBARO Manuals

Now the smart module has been wired correctly (powered by 24V DC) to my ventilation unit, but I also had some RF controllers laying around, which was ready part of ventilation. As these are currently useless, I thought “hey, let’s try to use these to trigger te switches of the smart module”, and that’s where the pains began…

Essentially, my current wiring is such that when Q1 and Q2 should be open (i.e. no connection with IN), that there is a +23V signal arriving at S1 and S2 respectively. If this voltage signal then drops to 0V, it should close Q1 or Q2. However, nothing happens, irrespective of when a 23V signal is put over S1/S2 and N or not… As I understood it, this should at least flip Q1/Q2 (parameter 20 is set to value 2 for both switches), but nothing happens at all. Q1 and Q2 can be opened or closed at will using the Homey app though, so they are certainly responsive…

Can someone give some suggestions as to where I go wrong? Is the issue that the S1/S2 need a higher voltage in order to be switched? Or did I wire it incorrectly and should they not be connected to a + pole?
All feedback is welcome! Many thanks!