How to include a DNN in a Genetic Algorithm searched function

Hello MathWorks Team, I want to use GA to search best input of a certain function so that the function’s output could meet the desired value.

So I create a function to calculate the loss between actual output and desired value. Then I called GA to evaluate the function.Below is my loss function with a dummy function.

function Loss = ForwardPredictionLoss(SPratio,nref)
AA = reshape(nref,4,7);
A = AA*ones(7,4); % ones(7,4) is just some dummy function for test
B = SPratio;
err = (A-B).^2;
Loss = sqrt(sum(sum(err)));
end

and my main script using GA for function input searching:

SPratio = diag(ones(1,4));
nref = ones(28,1);
lb = -ones(28,1);
ub = -lb;
Options = optimoptions(@ga,'PopulationSize',25,'MaxGenerations',20);
[x,fval] = ga(@(nref)ForwardPredictionLoss1(SPratio,nref,FWNnet),28,[],[],[],[],lb,ub,[],Options);

So far, everything goes well. However when i tried to replaced the dummy function with a fixed DNN. I always get some error. Here is my code:

function Loss = ForwardPredictionLoss1(SPratio,nref,FWNnet)
nref1 = nref;
A1 = predict(FWNnet,nref1);
A2 = predict(FWNnet,nref1);
A3 = predict(FWNnet,nref1);
A4 = predict(FWNnet,nref1);
A = [A1 A2 A3 A4];
B = SPratio;
err = (A-B).^2;
Loss = sqrt(sum(sum(err)));
end
clc;clear; close all
load FWN
FWNnet = net;
SPratio = diag(ones(1,4));
nref = ones(32,1);
lb = -ones(32,1);
ub = -lb;
Options = optimoptions(@ga,'PopulationSize',25,'MaxGenerations',20);
[x,fval] = ga(@(nref)ForwardPredictionLoss1(SPratio,nref,FWNnet),32,[],[],[],[],lb,ub,[],Options);

Could you please share the right code for this.

Thanks so much.