[Closed] CreateInstance return NULL in lesson5a

Hey I have a problem creating simple meshes in lesson5a without modifications.

SampleGObject* myGeomObj = (SampleGObject*)ip->CreateInstance(GEOMOBJECT_CLASS_ID, SampleGObject_CLASS_ID);
INode* node = ip->CreateObjectNode(myGeomObj);
TimeValue t (0);
Matrix3 tm(1);
node->SetNodeTM(t,tm);

does crash max as node is NULLpointer
However
SampleGObject* myGeomObj = new SampleGObject();
does work but in this case max says unknown classID on save
Why is CreateInstance returning null?