A heartbeat event is a once daily check-in by a tracker to communicate that the device is powered up and capable of working. It does not transmit a GPS location. The tracker is alive!
Most but not all devices report heartbeat events. Devices that are programmed to check in every 12-24 hours with a GPS location do not typically report heartbeats.
'Power On' follows a heartbeat event on many devices. This is just indicating that the tracker has rebooted and can be ignored.
Columns such as "last communication" may show a timestamp that is from the heartbeat event occurring rather than the last event that included the most up to date GPS location.
Heartbeat events can be found in the "Event Detail" report. They are easiest to spot when a vehicle has not been used in more than a couple of days.
Consecutive heartbeat events would suggest the tracker has remained powered but the vehicle has not moved - or at least the tracker has not registered a change in location.
If only heartbeat events are showing for a particular tracker in a vehicle you believe has moved then the device may either need rewiring (for hardwired units) or special programming is needed (for plug in units) so that the device can detect ignition correctly.