Normal map appears to be wrong when generated

Hi

I am making a keyboard model on 3ds max for a unity project. I am trying to make a normal map baking for my model, with the "render to texture" functionnality. The work is almost done, but i have a mistake on the map. you can see the result here:

(click on the attached below, you will have a better shot)

The problem is that depending on the light is, the sides of my keys haves shadows, but all the same, like if they all receive the light from they front, or from they back at the same time.

I tried to play with the channel options, but i can't find a working setting. How can i fix this?

Thank you for reading.