Hi Paco,
I have a Fermex 3399 and was having trouble making it work.
I tried all sorts of ways.
Finally, I had overlooked the step in the instructions to actually disconnect the Opener from the ribbon cable, then wire it per the instructions, plug it back in to the Opener and complete the rest of the configuration steps.
Then it worked for me.
Now I wish the Apple Watch LTE could open the apartment main door all on its own without an iPhone!!