Hello!
I have a very stupid problem and i am not able to fix it.
I hope someone could help me! thanks in advance.
Lichunhong
The error message seems to indicate that Model Curves can only be planar
You can only create non-planar nurbs curves in certain Families. For example, if you create a new Mass Family, convert your points to reference points then use CurveByPoins.ReferencePoints() from the Revit library:
Thanks very very much 
@Thomas_Mahon @Vikram_Subbaiah