So I've been having some problems duplicating or creating new races. When I duplicate an existing race, or when creating a new race, I can't preview the model and the npc with the correspending copied race will be invisible. Can anyone help me point out the reason why this is the case?

You may need to set a Morph Race and Armour Race under Copied Data in the General Data tab in race properties?

Set Morph and Armor to the race you originally duplicated from, and then it should work.

Yes lots of thanks! That did it for me! =)