nidaqmx python example error message

Hi,

I'm trying to run the nidaqmx example shown bellow, using the NI USB-6008:

I've installed the python nidaqmx package and the NIDAQmx Runtime eviroment 18.10 under windows 10.

The examples are:

https://github.com/ni/nidaqmx-python/blob/master/nidaqmx_examples/ao_voltage_hw_timed.py

and

https://github.com/ni/nidaqmx-python/blob/master/nidaqmx_examples/ao_voltage_sw_timed.py

But I get the error message:

Traceback (most recent call last):
  File "ao_voltage_hw_timed.py", line 7, in <module>
    task.timing.cfg_samp_clk_timing(1000)
  File "C:\Users\LocalAdmin\AppData\Local\Programs\Python\Python36-32\lib\site-packages\nidaqmx\_task_modules\timing.py", line 3007, in cfg_samp_clk_timing
    check_for_error(error_code)
  File "C:\Users\LocalAdmin\AppData\Local\Programs\Python\Python36-32\lib\site-packages\nidaqmx\errors.py", line 127, in check_for_error
    raise DaqError(error_buffer.value.decode("utf-8"), error_code)
nidaqmx.errors.DaqError: Requested value is not a supported value for this property. The property value may be invalid because it conflicts with another property.
Property: DAQmx_SampTimingType
Requested Value: DAQmx_Val_SampClk
Possible Values: DAQmx_Val_OnDemand

Task Name: _unnamedTask<0>

Status Code: -200077

Any ideas why I get this message?

-Olli