About 50% of the time when I attempt to unlock my car using the proximity button on the door, it does not respond. I have to press the unlock button on the key fob. Then when I attempt to start the car, there is no response. If I again take the key fob out of my pocket and wait a few seconds, I'm able to start the car. Other times, I'm able to unlock the car and start it with the key fob in my pocket, but immediately after starting the car, the "no key" light flashes in the instrument cluster. These all seem like indicators that the key fob battery is dying. I don't know how long the batteries typically last in these, but mine is 3.5yrs old. After a few months of this issue, I figured it couldn't be an issue of a dying battery, since it's still working after all these months. Then it dawned on me. I keep the key fob and my cell phone in the same pocket. I started keeping my phone in a different pocket and wouldn't you know, that solved the problem! Apparently the electromagnetic field the phone gives off interferes with the proximity key signal.
I wanted to share this story with everyone in case others are experiencing similar no entry, no start issues. It was a very annoying! Glad it was something simple.