In MPC toolbox, find function 'plotstep(plant)' cannot work exactly?

Recently, I am learning to use MPC toolbox, and when I follows the examples in my book, I find that the function plotstep(plant) does not work just like the examples shows. The problem I noticed is that the function plotstep(plant) can't exit itself once called, and of course it cannot give the entire answer(figure) when I applied it to an MIMO plant. So I am wondering if there is any change in the function or it has substitution in MATLAB now? Or it's a existing bug? Thank you brilliant guys!

PS: My MATLAB version is R2016b.

codes:

    num1=2;den1=[1,1];num2=3;den2=[1,2];num3=1;den3=[1,4];num4=1;den4=[1,1];
    for i=1:4
       eval(['tf',num2str(i),'=poly2tfd(num',num2str(i),',den',num2str(i),',0,0);']);
    end
    plant=tfd2step(5,0.1,2,tf1,tf2,tf3,tf4);
    plotstep(plant);

Answer 1

[jeap]

Well, I checked the code of function plotstep(plant) and get the point. There is a pause segment inside!