2007 Nissan Altima Brakes and Steering wheel

Try inserting the prox key (or smart key which ever it is named) in the slot for it. This slot is usually located on the driver side dash on bottom side or in the center console compartment. If you have more than one key try all the prox keys you have.
It sounds like you have an issue with the vehicle recongizing the prox key or in other words the vehicle's security system is not allowing the engine to start.
Are batteries inside the key in good condition? Try replacing the batteries may help. I think most modern Nissans will tell you the battery level in the instrument cluster.
Try these things and get back to me. Thanks for the question