Call Tesla and ask them to poke it. This is assuming you’re not in a cellular dead zone. My old ‘13 S85 with 3G had an issue with connecting a couple times. Signal was good. App wouldn’t connect but Tesla was able to see the car and poke it.
Got the 50.2 on Christmas Eve. Car needed me to sit in it and fire it up again to connect. I've never seen the "systems are starting up" message in the instrument cluster before - main screen was dead. No heat etc... Finally, after a few minutes of me pressing the brake pedal and steering wheel buttons, the car fired up again. Odd. I did nothing different in settings etc... to cause this behavior.