Verify the solid bodies and their materials.
In Mechanical's Outline under Model, expand Geometry.
There are three bodies, but here you are interested only in the two unsuppressed solid bodies:
FEA\Valve: This is the reed valve, which opens and closes with positive and negative air flow, respectively.
FEA\Stopper: This is the stopper, which mimics the wall of the domain onto which the valve would settle, providing a physical representation of where the valve stops.
Verify the material for each of the solid bodies.
Under Geometry, select the body.
In the Details pane under Material, confirm the Assignment value is set to Stainless Steel.