S7-200, EM231 TC module, temperature reading error

[Swissi]

Hi all
Please I need your help
I have qty#4 EM231 thermocouple modules, each module is 8 inputs, all are used with cpu226, the temperature reading on HMI are all wrong, the sensors output millivolt to TC modules inputs are normal, but the temperature readings is wrong and showing minus values. I contacted the machine manufacturer but couldn't get much help, and couldn't get plc project password.
The cpu working normally, no error led.
This machine was not used for 7 months and now after started, this problem happened. I replaced one EM231 with other spare one but it's still the same issue, There is no calibration gain potentiometer on this module .
I really appreciate any help you could supply.
My regards