cut and fill

Good Day,

I have done the cut and fill couple times and it usual works. now i have a pointcloud made a terrain from it and removed the point cloud then made the terrain active. 

this terrain model i referenced in my 3d file and now i try to determine the cut and fill. usual it works but now it keeps giving me the outcome that my existing surface is not available.

i tried to make the terrain with a 2d 3d file and with just a 3d file i made it active in both reference as modelfile. it shows in cross sectiosn but still it says that the existing surface is not available.

Anyone  has a clue what i might  have done wrong, i done this before on different model.