Nikhil Narale
Ansys Employee

That's okay. But when switching to transient, you also have to set the simulation parameters (number of time steps, time step size, ...) correctly. What I can see is you have set number of time steps = 0, which is not letting you run the case. 

To know more in detail, refer to this section of the Fluent's User guide: 32.13. Performing Time-Dependent Calculations (ansys.com)

If you are not able to access the link, refer to this forum discussion: Using Help with links (ansys.com)