I could not map my second floor either. I ended up buying a second one Now I have one on both floors and it is much easier than carrying everything up and down the stairs.
After you clean the first floor and you’re wanting to go to your second mapped or cleaned where there is no doc. Click on device and it will take you to what you just cleaned all over beside that. There is three little squares. I would call them squares click on the second one and down at the bottom of the page it will say multiple floors click on that and if you haven’t mapped, it go down past that and it will say create map if you have maps it it should show you that map , click apply and it will go to the data for that room or rooms , make sure your vacuum cleaner in the rooms you want to clean and click on it will create a map of that floor when you get ready to clean the second floor then you can pull up the second map and click apply and it will load the data for that second floor, I hope that makes sense.
