Call to sdm.devices.commands.ThermostatTemperatureSetpoint.SetCool fails with error 500 Internal Error

Question

I'm new to the Google / Nest SDM and saw this questions has been asked previously but not answered. I'm hoping with a little more information, I might be able to get some direction on where to look. I have been working on a connector app and I have most functionality working, I can retrieve the structures and devices and I can even change the modes from OFF to HEAT. to COOL and the thermostat reflects the changes. However, when I try to change the temperature, whether it's in heat or cool mode, I receive:

{
    "error": {
        "code": 500,
        "message": "Internal error encountered.",
        "status": "INTERNAL"
    }
}

I'm using:

{
    "command" : "sdm.devices.commands.ThermostatTemperatureSetpoint.SetCool",
    "params" : {
    "coolCelsius" : "22.0"
    }
}

I've tried Postman, RESTer and I don't receive much information other than the error 500. Anyone recommend anything else I can check? Weird how I can turn the thermostat on/off/change mode or put into ECO, but I can't adjust the temperature.