heres some notes i gathered from others who had issues
MALFUNCTION AFTER CHANGING BATTERY
Remove key from the back of key fob, press start button twice inside of car but be sure not to start the vehicle. Next get out of car and close the door, insert metal key into drivers side key slot on door handle and turn key to lock and unlock position once. Go back into car and shut off ignition by pressing start button once, ignition is now off. Problem fixed, this worked for me which saved me time and effort running back to the dealer. Note this may have to be done again when changing a dead key fob battery.
OR
I have two intelligent keys with the 2013 Altima S I just purchased and the buttons don't work on either one. The dealer had replaced the batteries and I replaced them once again. Clearly, the transponder is working. The request buttons on the door handles and trunk lid work when the key is in proximity.
The solution turns out to be very simple. Although there may be some other secret way to get the car to reprogram the remote control functionality, the brute force method that works is to simply do a cold reset of the ECU. The easy way to do this is to simply disconnect a battery terminal - wait several minutes - and then reconnect it again. Before reconnecting the battery again, make sure the keyfob is inside the car. The ECU apparently only attempts to reprogram the remote functions on a cold boot and if the key fob is not within range, it won't work.
Both of my remotes were dead and I did this on each one - one at a time. You might be able to do more than one at once, but I guessed it might be necessary to do one at a time.
Please note this only works to solve the problem of the keyfob remote buttons not working. I believe this is most likely to happen after changing the battery in the keyfob. If your door request buttons are not working, or you are getting other errors or problems when attempting to start the car, this will probably not help.