Hello .colas -
So there seems to be a few things that are happening with your model.
In the first image, inside of Maya, it appears as if you have seams everywhere. The thick green lines are indicative of where your geometry does not meet.
That’s the pre UE4 issue that I see.
Inside of UE4 make sure you have assigned the light map channel to your mesh inside of the meshes detail panel.
I am going to link you our lighting troubleshooting guide on our wiki.
This should help clarify/guide you with any lighting issues that could be occurring in your scene.
Thanks,