2 ways to fix it: the quick way and the right way.
quick way: select material in twinmotion with the eyedropper > settings > two sided on.
or
right way: _ShowDir in rhino to display the normal directions, and then from there fix the normals to point outwards using _Flip.
Hello ,
Thank you for posting in the community and @Emre Senoglu​ is correct with his suggestions.
Hope this helps you and others who face this problem.
Kind regards,
Vincent B.
Thank you so much