If you haven't done so already, it wouldn't hurt to factory reset the Hub rather than just rebooting it. Anecdotal evidence has suggested that this is sometimes necessary to kickstart DV upon first activation. With the Hub powered on, push the reset button with a paperclip & hold it until LEDs flash. It can take a while.
Thank you all for your help.
For those reading this thread- in our case it was a dodgy Hub…
The complaints team were very helpful and, given the data they were/ weren’t receiving from our Hub, they deduced this was likely to be the problem and posted a new one! The new one connected everything without a glitch.
Problem solved.