On some devices (especially Chinese) or Android versions, the TrackChecker Mobile application can not work in the background (sleep) mode. Select the "Wake up device" checkbox here "Settings" -> "Events updating", to output the device from the "sleep" mode, when updating events after a set period of time.

For Andorid 7.0 and higher, you also need to allow the application to work in the background in the Android system settings.