Switch not receiving signal RFXtrx433E

[AVB001]

I have a Klikaanklikuit AWMT-230 switch built in behind my regular double light switch but I can't switch the lights on using Domoticz. It's connected properly, according to the manual that came with it (https://www.klikaanklikuit.nl/media/wys ... 0048_1.pdf page 9).

Both swithes are visible in Domoticz and the logging is working nicely. Which means that when I manually turn on the lights a red light on the AWMT-230 blinks and I can see this (On/Off) in the Domoticz logfile.

But when I try to switch the lights on using Domoticz nothing happens, no red light is blinking, so I assume that the signal isn't received by the AWMT-230.

Does anyone have an idea of what I'm doing wrong?

I'm running Domoticz 4.9700 on a Raspberry Pi with a RFXCOM RFXtrx433E.