Nissan Sentra does not complete O2 sensor monitor

Good morning, I'm looking for help to solve my problem.
I have a 2011 Nissan Sentra, when scanning it, an OBD monitor reports incomplete.
To date I have not achieved the O2 sensor monitor, it does not report fault codes and the car works well.
I had the opportunity to scan two feelings of other years (2008 and 2010) and the O2 monitor did not mark complete.
I took it to the agency and suggested washing injectors, cleaning acceleration body and changing spark plugs although the manual suggests doing it every 100,000 miles, my car has 85000 kms.
I did all that and still does not complete the O2 monitor.
I started a complaint report in Nissan and the answer was that they can't, nor do they want to help me because the car is no longer in guarantee.
Thanks in advance for any orientation that can give me ...