Sorry, in fact it's working. I just needed to unplug my primary display and to plug the rift instead.
The feeling is there, this way better than DK1 but the details remain to low to be playable. I can't read anything on the hud, even if I lean toward the screen. I'm still not sure that CV1 with 1440p will be enough.
But it's fun for flying around, I almost feel like i'm in it.