A P0841 fault code means that the transmission fluid pressure sensor which monitors the hydraulic pressure inside of the transmission is not performing according to the preset parameters.
Here are some possible causes:
Not enough transmission fluid
Dirty transmission fluid
Failed transmission pump
Failing torque convertor
Transmission fluid pressure sensor failure
The most common one is not enough fluid. Unfortunately on your car, which is a CVT, there is no transmission dip stick to measure with. You'll probably have to go to a Nissan dealer to get it checked.