This message may appear when you solve a model with uncertainty and chance constraints using robust optimization. When you do this, the Solver transforms your original model with uncertainty into a robust counterpart model that is a conventional optimization problem without uncertainty.

This message means that the Solver could not find a feasible solution to the robust counterpart problem. It does not necessarily mean that there is no feasible solution to the original problem; the robust counterpart is an approximation to the problem defined by your chance constraints that may yield conservative solutions which over-satisfy the chance constraints.

When this message appears, there may be an option to “Auto Adjust Chance Constraints” – a small white button containing a green arrow, as shown below for result code 27. Your simplest course of action is to select this option and click OK. The Solver will then re-solve the problem, automatically adjusting the sizes of robust optimization uncertainty sets created for the chance constraints, in an effort to find a feasible solution.

If you don’t see the option “Auto Adjust Chance Constraints,” this normally means that the automatic improvement algorithm has already been tried (possibly because the “Auto Adjust Chance” option is set in the Task Pane), and this algorithm was unable to find a feasible solution. In this case, you should proceed as described for result code 5, “Solver could not find a feasible solution:” Look for conflicting constraints, i.e. conditions that cannot be satisfied simultaneously, perhaps due to choosing the wrong relation (e.g. <= instead of >=) on an otherwise appropriate constraint.