If the new data immediately follows the data used to design and test the net, the following syntax should have been used
[ net tr Ys Es Xsf Asf ] = train(net,Xs,Ts,Xi,Ai);
Xinew = Xsf; Ainew = Asf;
Ysnew = net(Xsnew,Xinew,Ainew);
Xinew = Xnew(:,1:d); Xsnew = Xnew(:,d+1:end)
but Ainew is not known.
I would try the mean of the previously used test target data rather than use zeros. Perhaps several designs using values in the interval [mean-stdv,mean+stdv] would be useful.
Hope this helps.
Thank you for formally accepting my answer