I have a Model 3, so not sure about the Model S, but I would delete and add again the phone App to the list of devices.
Note: I used recently the 'Airplane Mode' because I was in a meeting. So WiFi and Bluetooth got disabled.
Then when I turned off the 'Airplane Mode' I was able to open the door but not to start the car.
I rebooted my phone, which fixed the problem.
I will try to duplicate it to test and understand what really could be the issue.
But better to always carry a card to avoid been stranded.