smart key not working

I have 2007 Nissan Altima 2.5 and I'm having a problem with my smart key can't unlock or lock the door or the trunk, also can't start the car. To get in the car I have to use the key and to start the car I have to put the smart key in the charging slot in order for the car.to pick up the key. Any idea how to fix this? Thanks for help