My Roomba 960 is giving error 6 Even when it's on the floor

Hello Technicians if you know about the popular robot Vacuum “Irobot Roomba" then I need some help with mine.

So i had a Roomba model 960 for about 3-4 weeks now and it cleaned my house great but then yesterday afternoon I started to get an error 6 message I thought to myself “it was nothing ill just clean the cliff sensors and it work again” so then I proceeded to clean the cliff sensors thoroughly with the cloth and tried to get it back to work again but it's still giving an error 6 message (Quick note: If you don't know what error 6 Is its when your Roomba is near staircase and won't move and needs to be place somewhere else). So then the error message won't go away I've also cleaned the side brush and the rod that spins the brush also no change in effect I've also resetted/ rebooted my Roomba also did not help. So I don't know what to do next. So can you please tell me how to fix the problem because I want a nice Clean home again. Thanks for reading technicians hope you find a solution soon :)

P. S. I have contacted Irobot customer care/service/support and they said I should return it to the store I purchased it from and I wasn't able to because the return date expired also they can't accept any robots taken in.