What happens if the Temperature Sensor terminals are connected with the wrong polarity?

The measured temperature will not be displayed properly.

Thermocouples

If the polarity is connected in reverse, the Temperature Controllers will display a falling temperature when the temperature is actually rising.

Platinum Resistance Thermometers

If the polarity between A and B are reversed, "S.Err" will be displayed.
There is no polarity between B and B.

Make sure that the polarity and terminals are correctly connected.