Hi Mala, generally the natural direction of a curve does not matter in Moi because of stuff like the end nearest to where you clicked on it when selecting it is used rather than the default direction.

So although there is a "Flip" command it won't really do anything.

Some commands like Loft will automatically figure out directions but also have an option where you can click on one of the curves while at the Loft options stage to reverse it.

It's difficult to know what's happening in your specific case without seeing the .3dm model file, please post it here or you can e-mail it to me at moi@moi3d.com if you want to keep it private.

Thanks, - Michael