This commonly happens when your sensor battery is flat. Plug your sensors in to your USB cable and charge for at least 30 minutes, then try to turn the sensors on again.

It is recommended that when performing assessments, you have an amber to green level of charge on your sensors, as guided by the light indicator located on the side of the sensor, next to the MicroUSB cable port. 

If the problem persists, contact the dorsaVi support team.