Hi Baptiste,
Unfortunately you don't write which NI-DAQ Version you're using. I suppose that the NI-DAQmx version you're using doesn't support the PCI-6014. Do you see the PCI-6014 in MAX under "Devices and Interfaces>>NI-DAQmx Devices"? If you don't see it there, but under "Devices and Interfaces>>Traditional NI-DAQ Devices" only, then this would mean that you're using an NI-DAQ version which doesn't support this board under NI-DAQmx. I recommend you to uninstall the NI-DAQ version you're using and to install NI-DAQ 7.3. This version supports this board with the Traditional and NI-DAQmx (DAQ Assistant)driver. You can download the driver from our website.
Hope this helps.
Regards,
Luca