System identification for non linear grey box model - not working

I am trying to estimate parameters in my nonlinear grey box model. For that, I prepared my dataset and nlgr model. I am getting an error message when I am try to use compare or pem functions from sytem identification toolbox. I tried to debug the code and found out that the x and u vectors at time t=0 that are given to my nlgr model by compare or pem functions are just vectors containing ones. I tried to use a fixed initial conditions for the model but that also didnot work. I really appreciate if anyone can help me understand this problem.

Below is the model:

Time-continuous nonlinear state-space model defined by 'DMFC_Stack' (MATLAB file):

     dx/dt = F(t, u(t), x(t), p1, ..., p5, FileArgument)
      y(t) = H(t, u(t), x(t), p1, ..., p5, FileArgument) + e(t)

with 9 inputs, 5 states, 3 outputs, and 5 free parameters (out of 5).

Inputs:
   u(1)  Stack current(t) [A]
   u(2)  Fan speed(t) [%]
   u(3)  Molar flowrate of methanol into stack(t) [mol/s]
   u(4)  Molar flowrate of water into stack(t) [mol/s]
   u(5)  Molar flowrate of carbon dioxide into stack(t) [mol/s]
   u(6)  Concentration of methanol in fuel(t) [M]
   u(7)  Temperature of fuel entering ACH(t) [K]
   u(8)  Temperature of air entering CCH(t) [K]
   u(9)  Air flowrate(t) [SLPM]
States:                                 initial value
   x(1)  ACH temperature(t) [K]         xinit@exp1   323   (est) in [280, 350]
   x(2)  CCH temperature(t) [K]         xinit@exp1   321   (est) in [280, 350]
   x(3)  SM temperature(t) [K]          xinit@exp1   323   (est) in [280, 350]
   x(4)  Anode overpotential(t) [V]     xinit@exp1   0.3   (est) in [0, 0.6]
   x(5)  Cathode overpotential(t) [V]   xinit@exp1   0.3   (est) in [0, 0.6]
Outputs:
   y(1)  Temperature in ACH(t) [K]
   y(2)  Temperature in CCH(t) [K]
   y(3)  Voltage of stack(t) [V]
Parameters:                                                                           value
   p1   Heat capacity of SM [kJ/(kg.K)]                                               0.846   (est) in [0, 10]
   p2   Heat transfer coeff between upward surface of SM and ambience [1E-4 kW/K]      0.32   (est) in [0, 10]
   p3   Heat transfer coeff between downward surface of SM and ambience [1E-4 kW/K]    0.32   (est) in [0, 10]
   p4   Capacitance of anode charge double layer [F/cm^2]                                 4   (est) in [0, 20]
   p5   Capacitance of cathode charge double layer [F/cm^2]

Error:

x =

     1
     1
     1
     1
     1

K>> u

u =

     1     1     1     1     1     1     1     1     1

??? Error using ==> idnlgrey.isvalid at 165 Error or mismatch in the specified ODE file 'DMFC_Stack'. The error message is: 'Input to ROOTS must not contain NaN or Inf.'

Error in ==> idnlgrey.predict at 112 error(isvalid(nlsys, 'OnlyFileName'));

Error in ==> utcompare at 556 [yh{ksys}, x01{ksys}] = predict(th, z1, m, ksysinit);

Error in ==> idnlmodel.compare at 114 utcompare(v{:});