Solution:

Firstly, to work with PCI-1760, you need to install the 32-bit DLL driver higher than V1.10. Secondly, in the standard example, the program continually polls the PCI-1760 in high speed and that is too fast for the relay board PCI-1760 to respond. If we can prolong the polling period and the PCI-1760 can work normally. After testing, we have found that the PCI-1760 can work with Labview driver if we make some modification to the example. We can do that by simply add time-delay into the while loop, just like the following picture.