This message appears if you’ve selected the Simplex LP Solving method, but Solver’s numeric tests to ensure that the objective and constraints are indeed linear functions of the decision variables were not satisfied.

If you receive this message, select and examine the Linearity Report to determine which functions or variables in your model are not linear, then examine the formulas for the objective and constraints for nonlinear or non-smooth functions or operators applied to the decision variables. For more information, see Functions of the Variables.