Login to your account at Orange and go to "Manage your second line" the info is in there. If the "Manage your second line" entry isn't shown then I suspect it's not activated.
O ...
I've set up countless Liveboxes and VOIP for others and I always call the Orange help desk to activate the phone.
Have the serial no and the MAC address ready (on the base of the Livebox)
It's nev ...