I think the problem with my device is that the update from the Onyx page and with the one underscore linked to is that they are for the Nova... NOT the Nova Pro.
Using that update would likely work to roll a Nova device back to the previous firmware, but not so for a Nova Pro which has some different hardware related to the stylus.
So it is probably a very good thing that the package failed to verify, otherwise it might have caused some significant issues. Will have to be more careful about installing or attempting to install new updates in the future.