The affect of air flow on cantilever

I'm working on a project on COMSOL to study the affect of flow on cantilever, I used laminar flow and solid mechanics in my model. I drew the cantilever with fixed end in a box.
two surfaces of the box have been identified as the inlet and the outlet of the flow.and the cantilever in the center of the box.

The error I'm getting is :

cannot evaluate expression
Failed to evaluate expression
Expression: mod1.spf.U
failed to evaluate variable.
variable: mod1.spf.U
- Geometry : 1
- Boundary : 9
- Plot: surf1 ( surface )

while boundary 9 in my model belongs to the cantilever( the fixed one )
Please, I need an urgent help desperately as the project should be submitted by Thursday.
I attached the model that I did.
Thanks a lot in advance