I can't get this code to run. Does anyone have any suggestions?

//Preamble

var y;

varexo e;

parameters alpha sigma;

alpha=0.75;

sigma =1;

//Model

model;

y=1+ alpha*y(-1) + e;

end;

initval;

e=0;

y=4; //ybar=1+0.75ybar => solve for ybar=4

end;

steady;

check;

// Shock section

shocks;

var e;

stderr sigma;

end;

stoch_simul(order=1); // Or stoch_simul;

What is the error message?