从GAMS官网下载的GAMS后怎么用不起来？我按照指南例题，照葫芦画瓢
sets
i /seattle,san-diego/
j /new-york,chicago,topeka/;
parameters
a(i) /seattle 350
san-diego 600/
b(j) /new-york 325
chicago 300
topeka 275/;
table d(i,j)
seattle san-diego topeka
new-york 2.5 1.7 1.8
chicago 2.5 1.8 1.4;
scalar f /90/;
parameterc(i,j);
c(i,j) =f*d(i,j)/1000;
variables
x(i,j)
z;
positivevariable x;
equation
cost
supply(i)
demand(j);
cost.. z=e=sum((i,j),c(i,j)*x(i,j));
supply(i).. sum(j,x(i,j))=l=a(i);
demand(j).. sum(ij,x(i,j))=g=b(i);
model transport /all/;
solvetransport using lp minimizing z;
display x.l,x.m;

之后，运行错误。特别是提醒license file validation failed,
截图在附件。高高手帮忙看看