Usually the unimesh fits require the basic outfit in order to work - the one you linked to requires the Space Dwellerfor M4 outfit.  I don't know about this one specifically but I have some other unimesh fit outfits and they work fine in Carrara; I used this one Menswear 1930's Unimesh in a render not too long ago and it not only loaded fine, it auto-fit to Gensis 2 Male almost perfectly.