Problems with ODE system using ode45

I would like to solve (and then plot the solution of) the Ordinary Differential Equation system

with initial conditions

.

Note that one needs to choose in order to make sense of the equations for . My first attempt is to choose them constantly such that

I tried to implement this system in Matlab.

First, I wrote the function myODE for the right hand side of the system; then I tried to used ode45. The code can be seen below.

Unfortunately, there seems to be a mistake because the plot only shows the initial conditions and, moreover, the time range is from -1 to 1 (see the following image) which is not what I would like to plot.

Where is the mistake in my code?

Can you help me, please?

function dxdt = myODE(t,x,lambda,mu,y0,y4) % 
% y0 = leftmost outer neighbour (constant)
% y4 = rightmost outer neighbour (constant)

dxdt = [exp(lambda*(x(2)-x(1)))+exp(mu*(x(1)-y0)); ...
exp(lambda*(x(3)-x(2)))+exp(mu*(x(2)-x(1))); ...
exp(lambda*(y4-x(3))+exp(x(3)-x(2)))];

%%%%% Next: Try to use ode45:
%%% arbitrary choice of lambda, mu, y0 and y4 just for testing the code
 lambda=1;
 mu=1;
 y0=0;
 y4=50; 
 % initial conditions: y_1=5, y_2=10, y_3=15
 % consider 100 time steps

[t,X] = ode45(@(t,x) myODE(t,x,lambda,mu,y0,y4),[0 100], [5; 10; 15]);

% plot x_1=X(1), x(2)=X(2), x(3)=X(3) against t
 
plot(t,X(:,1),'-o',t,X(:,2),'-o',t,X(:,3),'-o')

xlabel('Time t');
ylabel('Solution x');
legend('x_1','x_2','x_3')