Hi Florent,
did you make sure to export the e57 as ordered, so that RC can determine each scanner position? If it is only on file, then there can be severe problems which would explain the failing to align scan and images.
How did you take your images? It sounds like you are taking panorama shots from a few standpoints. Also, large parts of your object have less than ideal surfaces where RC probably has only very few tie points, if at all. You can check that in 2D view by activating Tie Points in the blue Image menu.
I’ve heard people claim that it also works with intensity only. My guess is that that depends on the object, since for some surfaces RGB and intensity are probably close enough for RC to identify some common tie points. In theory, you only need a handful of matches for a general alignment. I was going to try it out soon myself - if you get there first let us know how it goes! I would pay attention to small detail though because it could well be that there are larger deviations from the scan in areas where the texture does not allow RC to find matches.