k-e turbulence equation in coefficient form PDE

Hi,

I am working on gas solid fluidized bed in Euler-Euler model laminar flow Module. The run is fine.
Now I want to add k-e turbulence equations in Coefficient form PDE and solve the problem with consideration of turbulency.

It gives below error.

Undefined value found.
- Detail: Undefined value found in the stiffness matrix.
There are 3216 equations giving NaN/Inf in the matrix rows for the variable mod1.ep.
at coordinates: (0,0.418638), (0,0.427951), (0,0.437263), (0,0.446627), (0,0.455991), ...
and similarly for the degrees of freedom, NaN/Inf in the matrix columns.

Can anybody help me on this?
I appreciate any help.

Regards,
Loni