Did you call "HP816x Initialize.vi" first? You should wire the instrument handle output from Initialize to the input of Get Module Status.
If you still can't get it to work, post your code. Unfortunately, I don't have an HP816x to test it with, but maybe we can see something wrong just by looking at your VIs.
Unfortunately, this contributed driver (i.e., not written by NI) has sort of a weird architecture. The examples aren't very good; they don't teach you how to use the driver. The driver's documentation also appears to be written for C instead of LabVIEW.
Brian