If the optimization exercise does not get started, there are a number of potential causes:

1. There is some error in the model. Check all inputs and run in Simulator.
2. The value of the objective function is not improved by changing any parameters, this could be due to:
   1. Poor definition of the objective function. The objective function is not sensitive to the parameters selected. Try a different objective function.
   2. Poor initial guesses for parameters (e.g. very low or high values, such as 1e-10). Run the model in Simulator to find parameter values that have some effect on the objective function.
   3. Inappropriate selection of the parameters to be varied. Check the model and make sure that the parameters selected will affect the model results. Run the model in Simulator to check this.
   4. A selected parameter has been imposed on the Process or Data sheet in the Excel model. Changing the parameter value will therefore have no effect on the simulated result, as the profile will override any parameter value changes.
3. The model runs very slowly. Check this in Simulator. Click here for further help on slow-running models.