Examining your sensor’s data on our end shows that your sensor had low uptime for quite some time. You can see this by setting the map’s data layer to “Sensor Uptime” and increasing the averaging period to show more data on the map graph.
This could have been caused by frequent network interruptions or power issues. However, since the serial output showed a reboot soon after powering on, power issues are the likely cause. If the same power cable is being used to power your sensor, then I suspect that reflashing firmware is what may have resolved the problem.