Don't call the start method inside an ordinary Activity. Call this as higher as possible inside the class that extends android.app.Application exactly as shown above. This is the right place to call things that must survive for the whole application lifetime. Also, this is going to be called again if your application was restarted by the android system or anything else.
You can find the Upload Apk button in the menu bar at the Pushlink dashboard.
Don't forget or your installation will fail:
1 - Don't forget to upload to Pushlink a full signed release APK. It's a common mistake uploading development/debug APKs. Also, remember to checkV2 (Full APK Signature)in the Android Studio release wizard (Android 11 requirement).