The Tesla App is kinda iffy on android, although it's gotten much better. I've learned that the app takes forever to connect to the car if it's already open. You have to completely close the app by swiping the app away in the recent app drawer or press the back button until the app exits, and then reopen the app. You can't just press the home button to exit the app. If you see the red Tesla logo splashscreen, you know the app has completely reopened and it should connect quickly. It may also take a long time to get connected to the vehicle if your car has a weak data connection, such as parking in an underground parking structure.
Also for the interior temperature, you just gotta be a bit patient. The app has to poll the car for the interior temp via Tesla's server, then the car has to relay that back to your phone via Tesla's servers. This process can take a while for the interior temp to be reflected on the climate screen on the application especially when the app just connected to the car. It may also take a few moments for the HVAC to reflect that it is turned on after you turned initiated it from the mobile app. The interior temp should always be showing, but it takes a while to retrieve that info from the car.