Why Struct contents reference from a non-struct array object occurs?

I'm new to MatLab. Trying to connect MatLab and Unisim Design.

load('p_rez','p');
N=12;
M=1679616;
h=actxserver('UniSimDesign.application');
fl=h.ActiveDocument.Flowsheet;
flow=fl.MaterialStreams;
N2=flow.Item('Nitrogen');
CO2=flow.Item('CO2');
H2S=flow.Item('H2S');
Methane=flow.Item('Methane');
Ethane=flow.Item('Ethane');
Propane=flow.Item('Propane');
IButane=flow.Item('i-Butane');
NButane=flow.Item('n-Butane');
IPentane=flow.Item('i-Pentane');
NPentane=flow.Item('n-Pentane');
Feed=flow.Item('Feed');
for i=1:M
   N2.MassFlowValue=p(i,1)/3600;
   CO2.MassFlowValue=p(i,2)/3600;
   H2S.MassFlowValue=p(i,3)/3600;
   Methane.MassFlowValue=p(i,4)/3600;
   Ethane.MassFlowValue=p(i,5)/3600;
   Propane.MassFlowValue=p(i,6)/3600;
   IButane.MassFlowValue=p(i,7)/3600;
   NButane.MassFlowValue=p(i,8)/3600;
   IPentane.MassFlowValue=p(i,9)/3600;
   NPentane.MassFlowValue=p(i,10)/3600;
   Feed.PressureValue=p(i,11);
   Feed.TemperatureValue=p(i,12);
   VP(i)=Feed.VapourFractionValue;
end    
save('VP_Rez','VP');    

and here is an error

"Struct contents reference from a non-struct array object.

Error in FromUS (line 6)

fl=h.ActiveDocument.Flowsheet;"

What am I doing wrong?

[Walter Roberson]

What happens if h.ActiveDocument is empty ? You do not appear to be telling UniSimDesign to load or open anything; it might not happen to have anything active.

[Elina K]

So I need a load command for Unisim? How can I do that?

[Walter Roberson]

It looks like you would use h.GetObject() to load an existing case such as is shown near the bottom of the page I-9 at https://sites.ualberta.ca/CMENG/che312/F06ChE416/HysysDocs/AspenHYSYSCustomizationGuide.pdf