The delay typically happens at installation areas with a spotty cellular network connection. In such a case the sensor continues to collect data, while it attempts to reconnect. The following can be done to troubleshoot the problem:
Power cycle your sensor by removing it from the ground, placing the magnet back on for 5 minutes, and removing it again. You should see flashing white and then green. You can then reinstall following standard procedures.
If still not green, go ahead and leave the magnet on overnight and remove the magnet the next day. If you still do not see flashing white or green, indicates that there is an issue with the sensor.
If the above steps do not resolve the issue, please contact Customer Support.