@john.davey.home
An idea just occurred to me of something you might try.
I was talking to one of the 3DConnexion developers at a conference several years ago.
He tipped me off that unplugging connector (this is for Space Navigator, not sure about any other models) and then while holding both side buttons in plug it back in while keep holding for 5 seconds. This resets something in the Navigator itself.
I have about 50 of these things and this tip helped me get a couple of troublesome units working again.
Edit: I just tried on another machine and could not get it to work except when in an Active Sketch. When I Finished Sketch it would no longer work...
Edit 2: In my previous test I did not restart Fusion. Ran another test without Fusion running. Plugged in while holding the two buttons for 5 full seconds. Started Fusion. It is now working fine on this computer as well.
Edit 3: Tried on a 3rd machine and it worked fine without any additional steps.