Issues with SEN0159 CO2 sensor

I followed your sketch example for the SEN0159 CO2 sensor. It's powered by a 9V/2A DCexternal power supply more than 48h and it still reads 2.79V on the analog ouput pin even if i exhaust on the sensor during long time, nothing happen.
Can you explain me why i cannot observe CO2 variations ? Is there troubles with the board ?

Thanks!