Okay, resolved https://forums.dolphin-emu.org/images/smilies/smile.gif
In the end I changed the way to configure it.
I don't know why but it's a method that is boring to configure it now.
I need to leave Mouse/Keyboard as Device, and when I want to attribute a button of the wiimote or nunchuk to tha Rumble Pad 2 I need to right click on the button I want to change, select the RP2 as device for him, select the axe/button I want to attribute in the list of the RP2 buttons and axes available, apply and click OK.
This way the configuration menu doesn't just tell which button is used, he start by showing the name of the Device, so he really considere it.
Tried it and it works.
The problem is that it's harder to configure, takes time, and it's easy to choose the wrong axe for sticks.
In the end I changed the way to configure it.
I don't know why but it's a method that is boring to configure it now.
I need to leave Mouse/Keyboard as Device, and when I want to attribute a button of the wiimote or nunchuk to tha Rumble Pad 2 I need to right click on the button I want to change, select the RP2 as device for him, select the axe/button I want to attribute in the list of the RP2 buttons and axes available, apply and click OK.
This way the configuration menu doesn't just tell which button is used, he start by showing the name of the Device, so he really considere it.
Tried it and it works.
The problem is that it's harder to configure, takes time, and it's easy to choose the wrong axe for sticks.