When using the built-in functionality of a VINT port (Digital Input, Digital Output, VoltageRatioInput, or VoltageInput) you need to use setIsHubPortDevice(1), so it knows that it's opening the port itself, and not a VoltageRatioInput channel belonging to a device connected to that port. You'll still have to set HubPort, but not channel.
This video may help clear up the different cases of opening channels.