If the connection state in the raw data page shows 'offline' this means that your vehicle was not connected to Tesla's servers and data could not be obtained by TeslaFi.
This may occur if there was a connection issue with the cellular or wifi connection or there was a temporary issue with the vehicle's computer. Usually a temporary issue of offline resolves itself after a short while but if you continue to see offline issues a reset of the vehicle's computer may help by holding down both scroll wheels on the steering wheel until the screen restarts.
If 'Offline Asleep' is noted in the the raw data page under the note section this means that the offline session is being considered a sleep session. Some software versions report the vehicle as offline when idling instead of asleep so TeslaFi will consider the vehicle sleeping in this case. This settings can be adjusted in Sleep Modes->Advanced->Show Offline As Asleep.
Offline Alerts can also be configured in Settings->Notifications to send an alert when the vehicle has been offline for a specified amount of time.
Customer support service by UserEcho