Batteries, either the 12 volt or the key fob. You can self test the 12 volt on your car, there is a lot of info on how to do that in this site.
How old is your key? Most likely the battery in the remote. Cheap fix under $5. It should be a a 1632 watch battery. They are easy to open and replace. Take out the key, the end fits in a slot in the bottom of the fob, twist it and it's open and you have access to the battery.
As you posted the same question in the maintenance and troubles, have you tried (if you have one) the other smart key? Have you tried new batteries? It would be kind of you to reply to both. Many would be interested to know what you discover.
Not quite !!! if 12V battery is discharged you CAN NOT start the car. Touching the Ready will not help that.
I had the same problem as the op, but after "starting" the car that way and driving it some distance the problem never happened again. From that I assumed the 12v was low, though not completely discharged. It was just an assumption, I guess it could have been something else.
