Undefined Variable with structured grid

Hi all,

I am a new user of COMSOL. I am trying to implement a vector transport equation with Discontinuous Galkerkin FEM method. When I used free tetrahedral meshes the simulator works fine. However, when I tried to use a mapped structured mesh I found the following error

Undefined variable.
- Variable: comp1.M1
- Geometry: geom1
- Boundaries: 1, 2, 3, 4, 5, 6

It seems that there is an error with the definition of the variable in the boundary when using structured mesh.

Any help would be greatly appreciated and also suggestion regarding the design are also welcome.
P.S. For some reason I am unable to attach .mph file and the message I am receiving is "File extension error". The file size is only 48 KB.