Do not apply a Boundary Condition of Temperature to the Product wall. That forces the solution to keep it at that temperature through all time, which is what you got. Delete that Boundary Condition.
The product and the air should both get an Initial Condition of 3 C to start the simulation, then the convection from the warm air outside the box will heat the air inside the box and the airflow will heat the product over time.
Where is your small edge on the box defined as the Pressure Outlet to accommodate the increase in air volume as it warms up?