I had bought a 2nd D5 and given it to my mother-in-law, who used it offline for 7 years. She no longer needs it so I got it back, replaced the battery, and added it to the Neato app (still 3 years to go on their 5 years). I've got it to map a floor plan and everything, so it's working.
I just tried to add it to Hubitat via @gassgs's app from here. My older D5 was already there. I re-authenticated to Neato's servers, but when the app sends the /users/me/robots API call, it gets a blank 406 response:
Right after that, the app deleted my original D5 device from Hubitat.
I do see that my HA picked up the 2nd D5, so I know Neato's API are still working. I wonder if there is something else now required in the API call.