What does it mean when the GEKKO solution is not converging to a small enough value?

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When the GEKKO solution is not converging to a small enough value, it means that the optimization process is not able to find a solution that meets the desired criteria or constraints. There could be a number of reasons why this is happening, including poorly chosen initial conditions or constraints, insufficient optimization settings, or numerical issues with the solver algorithm. It may be necessary to adjust the optimization settings or constraints, re-evaluate the objective function, and/or try a different optimization algorithm to improve convergence.