If its V4.
When you merge in new data it will be in its own set or multiple new sets.
If you go to sets and list all the sets do you see any additional ones.
maybe the color is the same as your background color. Try changing color of background.
or if you are merging in a file that has been saved in a different wsp than master, it may merge the data in, but it will come in as a detail in the model library but no where in space geometry.
Thats all I can think of, without actually having the data.