Tessie works by getting data from Tesla about your vehicle as you're driving and charging.
If data is missing, it means the vehicle isn't sending the data to Tesla. This can happen when outside of cellular data range or when the connected cell tower or hotspot has an issue.
If the vehicle had a data connection but still didn't report the data, it means the vehicle is experiencing a firmware bug. You can fix it by restarting the vehicle. If the issue persists, perform a power cycle. After restarting, tracking will resume working accurately.
Looking for old data?
Tesla vehicles do not store historical data, so it's not possible to retrieve drives or charges from before activating Tessie.