Error Flag -20 in MLE+

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Greetings. I have trying to simulate a 1-zone building in Energyplus using MATLAB via MLE+ to apply RL. However, the "ep.read" throws an error: "Error using mlep/read EnergyPlusCosim: EnergyPlus process sent flag "-20" (Simulation terminated due to an error during the time integration). Check the D:*\eplusout.err file for further information.Check the .err file for further information*." The .err file is empty. I tried changing timestep per hour, no luck. Any suggestion to fix this? thanks in advance.