The external sensors that you are having problems with, are they self made or are they sensors from Pico. If they are the latter have you made a scaling file. Check that the wires have been set up correctly.
If the sensors are pico products test these on a different PC with the DrDAQ, if they still do not work, and you have another DrDAQ try the sensors with these otherwise the sensors will have to be returned to use for testing and investigation.
If you need to return them please provide contact details, by emailing: