cannot demodulate correctly, what am I doing wrong?

clear
close all
clc
%% defines the functions and their periods
syms t n t1 t2
One(t1,t2) = heaviside(t-t1) - heaviside(t-t2);
u(t) = heaviside(t);
r(t) = t*u(t);
A = 1;
t0 = 1;
m1 = A/(5-t0);
m2 = -A/t0;
m3 = -A/(5-t0);
m4 = A/t0;
y  = m1*(r(t)-r(t-(5-t0)) ) + m2*(r(t-(5-t0))-r(t-5) ) + m3*(r(t-5)-r(t-(10-t0))) + m4*(r(t-(10-t0))-r(t-10));
   
T = 10;
I = [ 0 T ]; % Intervals per row
figure
fplot( t , y , [0 , T] )
title('Original Function')
xlabel('t')
ylabel('v(t)')
grid minor
  
%% Complex form
% Number of harmonics
N = 24;
for i = 1 : length(T)
    
    % The symbolic Coefficients
    Cn(i) = (1/T(i))*int(y(i)*exp(-1j*(2*pi*n*t/T(i))), t, I(i,1), I(i,2));
    
    for j = 1 : 2*N+1
        
        nj = -N+(j-1); % it goes from -N to N passing through 0
        w0i = 2*pi/T(i);
        
        % The numeric Coefficients
        CnV(i,j) = eval(limit( Cn(i) , n , nj ));
        
        if nj < 0
            
            Exp(i,j) = 2*abs(CnV(i,j))*cos( -w0i*nj*t - angle(CnV(i,j)) );
            
        end    
    end    
    
    % The fourier series is coseine expresion, [-N,-N+1,-N+2,...]
    FS(i) = sum( Exp(i,:) ) + CnV(i,N+1);
    
end

%%plots the frequency spectrum  and the fourier signal
figure
subplot(2,2,[1,3])
fplot( t , FS(1)  )
title('Fourier signal')
xlabel('time')
ylabel('Signal')
grid minor

subplot(2,2,2)
stem( -N:N , abs(CnV(1,:)) ) 
title('Magnitude')
xlabel('n')
ylabel('|C_n|')
grid minor

subplot(2,2,4)
stem( -N:N , angle(CnV(1,:)) )
title('Phase')
xlabel('n')
ylabel('\angle C_n')
grid minor



Am=5; % Amplitude of modulating signal
fa=2000; % Frequency of modulating signal
fc =10*fa;
Ta=1/fa; % Time period of modulating signal
t=0:Ta/999:6*Ta; % Total time for simulation
ym=Am*cos(2*pi*fa*t); % Equation of modulating signal
figure(3);
subplot(3,1,1);
plot(t,ym), grid minor;
title ('Carrier Signal');
xlabel ('Time(sec)');
ylabel ('Amplitude(V)');


m =.5;

Ac=eval(FS);

y=Ac.*(1+m.*sin(2*pi*fa.*t)).*sin(2*pi*fc.*t);
%modulated signal
subplot(3,1,2);
plot(t,y);
title ('Modulated Signal');
xlabel ('Time(sec)');
ylabel ('Amplitude(V)');
grid minor;

md = y.*(cos(2*pi*fc.*t));
[b,a]= butter(2,0.1);
mf = filter(b,a,md);
subplot(3,1,3);
grid("minor");
plot(t,mf);

fs=45e3;
x = y.*cos(2*pi*fc*t);
[b,a] = butter(5,fc/fs);
x = filtfilt(b,a,x);
figure(4);
plot(t,x)
grid("minor")

xx = demod(y,fc,fs,"amssb");
figure(5);
plot(t,xx);

[Arrian Esteki]

I am supposed to get the same signal back that is exactly like the carrier but for some reason just showing modulated singal again