Alexa will always follow the minimum and maximum temperatures you have set on your ecobee4. So, if your minimum temperature is set to 60 degrees Fahrenheit, and you ask Alexa to change the temperature to 58 degrees, you’ll hear Alexa say this error message.
If you’re saying a temperature that is within your minimum and maximum, there’s a chance that your ecobee is set to Celsius instead of Fahrenheit.
To check if your thermostat is set to Celsius on your ecobee4 select MENU > SETTINGS > PREFERENCES.
To check if Alexa is set to Celsius, open your Alexa App or visit alexa.amazon.com then go to SETTINGS > DEVICE NAME (ecobee) > TEMPERATURE UNITS