ikey problem

[flex128]

Hello was searching and couldn't find an answer so decided to ask. I have a 2008 Altima SL sedan for some reason out of the blue the key light came on the dash saying battery was low I replaced the battery and the light still stays on at first it bothers me but since everything was working i ignored it.
Now about two months later my key won't unlock my doors or roll the windows down I have to use the key to unlock the doors then to start the car i have to insert the key into the slot that.
My question is am i having an issue where i need to just replace the Ikey fob or is it the sensor that reads it ? Any and all help is appreciated thank you in advance.

[Ace2cool]

I wonder if you didn't get a bad battery. See if your local auto parts store has one of those testers for key fobs, and if it picks up, then it would be something on the car side of things.