error nonlinear model fit

Hello All, I'm trying to use NonLinearModel.fit as below:

X = [mean_age_group1', TMI_group1']; %%Design matrix
Y = mean_FA_group1'; %%Response vector
FA_fun = @(b,x)b(1) + b(2)*x(:,1).^b(3) + b(4)*x(:,2).^b(5);
beta0 = [0.25 0.0005 1 -0.1 1];
mdl_FA = NonLinearModel.fit(X,Y,FA_fun,beta0);

But I receive the following error:

Error using internal.stats.getscheffeparam>ValidateParameters (line 182)
If non-empty, JW must be a numeric, real matrix.

Error in internal.stats.getscheffeparam (line 110)
    [J,VF,VP,JW,Intopt,TolSVD,TolE,VQ,usingJ] = ValidateParameters(J,VF,VP,JW,Intopt,TolSVD,TolE,VQ,allowedIntopt);

Error in nlinfit (line 433)
        sch = internal.stats.getscheffeparam('WeightedJacobian',J(~nans,:),'Intopt','observation','VQ',VQ);

Error in NonLinearModel/fitter (line 1123)
                    nlinfit(X,y,F,b0,opts,wtargs{:},errormodelargs{:});

Error in classreg.regr.FitObject/doFit (line 94)
            model = fitter(model);

Error in NonLinearModel.fit (line 1430)
            model = doFit(model);

Any idea what is the problem?

Thank you!