Could you please place the sensor under the sunlight for 2-3 days to charge it up? If the weather not good, it may take longer time. Also, Do you have an incandescent lamp at home? If so, you can try to put the sensor under the incandescent lamp for 24-48 hours and it may come back to work.
Is there anything I can do, or is it broken? And I don't have an incandescent bulb.
Could you please send us email to email@example.com with your Netro account registered email and your shipping info? We will ship a replacement sensor to you.