DTMF encoder/decoder

Why is that this DTMF decoder doesn't give me any outputs but the encoder works well? Here is my code below. It is suppose to give me the key inputted in my encoder in the command window but it does not work somehow. e.g. If I type myDTMF_encoder ([2 3 1 2], 5, 200) in my command window, it should display it back, I dunno why won't it work while my encoder works fine, if I type that in the command window it will return a beeping sound which clearly indicates the encoder works, please help!

for decoder:

function [A] = myDTMF_decoder(key,mark,space)
% 
Fs = 8000;
mark=mark/1000;
space=space/1000;


t = 0:1/Fs:mark;
a = 0:1/Fs:space;
len=length(key)/(length(t)+length(a));

key=key(key~=0);
j=1;
for k=1:len
   for i=1:(length(key)/len)+1
       if (i==1)
           b(k,i)= 0;
       else
           b(k,i)= key(j);
           j=j+1;
       end
   end
end

n=len;
key='\0';

for k=1:n;
    temp=abs(fft(b(k,:)));   
    x=1:(Fs/2)*mark;
    [~,i]=max(temp(x));
    f1=(i/mark)-1; 
    i=i-10:i+10;
    temp(i)=0; 
    [~,i]=max(temp(x));
    f2=(i/mark)-1;
    if f1>1000
        var=f1;
        f1=f2;
        f2=var;
    elseif f1<1000
    end
   
    if ((f1>692) && (f1<720))
       f1=697;
         elseif ((f1>765) && (f1<800))
            f1=770;
              elseif ((f1>847) && (f1<880))
                 f1=852;
                   elseif ((f1>936) && (f1<960))
                      f1=941;
    end
                  
    if ((f2>1204) && (f2<1240))
       f2=1209;
         elseif ((f2>1331) && (f2<1360))
            f2=1336;
              elseif ((f2>1472) && (f2<1500))
                 f2=1477;
                   elseif ((f2>1628) && (f2<1660))
                      f2=1633;
    end         
            
    switch(f1);
       case{697};
           switch(f2);
               case{1209};
                   key='1';
               case{1336};
                   key='2';
               case{1477};
                   key='3';
               case{1633};
                   key='A';
           end
       case{770};
           switch(f2);
               case{1209};
                   key='4';
               case{1336};
                   key='5';
               case{1477};
                   key='6';
               case{1633};
                   key='B';
           end
        case{852};
           switch(f2);
               case{1209};
                   key='7';
               case{1336};
                   key='8';
               case{1477};
                   key='9';
               case{1633};
                   key='C';
           end
        case{941};
           switch(f2);
               case{1209};
                   key='*';
               case{1336};
                   key='0';
               case{1477};
                   key='#';
               case{1633};
                   key='D';
           end
    end
    A(k)=key;
    k=k+1;
    
end

for encoder:

function [xt]=MyDTMF_encoder(key,mark,space)
%UNTITLED2 Summary of this function goes here
%   Detailed explanation goes here

Fs = 8000;
s=0:1/Fs:mark/1000;
p=0:1/Fs:space/1000;
xt=0;
z=0*p;

for i=1:length(key)
    switch(key(i))
        case(1)
            X=sin(2*pi*(1209)*s)+sin(2*pi*(697)*s);
        case(2)
            X=sin(2*pi*(1336)*s)+sin(2*pi*(697)*s);
        case(3)
            X=sin(2*pi*(1477)*s)+sin(2*pi*(697)*s);
        case(4)
            X=sin(2*pi*(1209)*s)+sin(2*pi*(770)*s);
        case(5)
            X=sin(2*pi*(1336)*s)+sin(2*pi*(770)*s);
        case(6)
            X=sin(2*pi*(1477)*s)+sin(2*pi*(770)*s);
        case(7)
            X=sin(2*pi*(1209)*s)+sin(2*pi*(852)*s);
        case(8)
            X=sin(2*pi*(1336)*s)+sin(2*pi*(852)*s);
        case(9)
            X=sin(2*pi*(1447)*s)+sin(2*pi*(852)*s);
        case(0)
            X=sin(2*pi*(1336)*s)+sin(2*pi*(941)*s);
        case('*')
            X=sin(2*pi*(941)*s)+sin(2*pi*(1209)*s);
        case('#')
            X=sin(2*pi*(852)*s)+sin(2*pi*(1477)*s);   
        case('A')
            X=sin(2*pi*(697)*s)+sin(2*pi*(1633)*s);
        case('B')
            X=sin(2*pi*(770)*s)+sin(2*pi*(1633)*s);
        case('C')
            X=sin(2*pi*(852)*s)+sin(2*pi*(1633)*s);
        case('D')
            X=sin(2*pi*(941)*s)+sin(2*pi*(1633)*s);
        otherwise
    end
    xt=horzcat(xt,X);
    xt=horzcat(xt,z);
end

sound(xt,Fs)
myDTMF_decoder(key,mark,space)
end