//check status CCS811 sensor
//CCS811Core::status returnCode = sensorCCS811.begin();
//if (returnCode != CCS811Core::SENSOR_SUCCESS)
==> add this line, and uncomment the above code lines, to have it work with the latest library sparkfun 2.0.3 CCS811
//check status CCS811 sensor
if (!sensorCCS811.begin())