2009 Santa Fe key question

Can someone help me answer a question about how the keys work for a 2009 Santa Fe? I have the two separate keys, old fashioned manual key and separate push button remote. When the battery dies on the car (eg due to light being left on), the remote doesn't work but the manual key doesn't open the driver side door. They key works perfectly fine for starting the car. Is there something I'm missing? Much thanks!