Pure Thermal examples not working

When trying to run the example lepton_get_object_high_temp.py, I get an error.

Runtime error: sensor control failed, pointing to this line:

sensor.ioctl(sensor.IOCTL_LEPTON_SET_MEASUREMENT_MODE, True, True)

None of the examples work for me on this board, what am i doing wrong?
Thanks for any pointers.
Andy