The computer on the key chain is not computing with the car what could be the problem?

Dead battery

Dear Sharon, there is no computer on a key chain to compute with your car, w/e that means.... Your probably talking about your key fob. Most likely the battery is dead and needs to be replaced (go to Walgreens and get a replacement) or it got deprogrammed and you would have to get the car (via spare key) to a nissan service center and have them reprogram the key fob