There are several reasons why your graphs may be flat.
The actigraphy is almost flat
If you can see some movement on the actigraphy, but the graph is unusually flat: . Sonar - make sure the signal is strong enough by keeping the sonar volume at max at Settings → Sleep tracking → Test sensor → blue sliding bar. - You can also try a different frequency by selecting other frequency from the drop-down menu list in Settings → Sleep tracking → Test sensor → Frequency - Keep the phone closer to your bed. - Try different positions of the phone. . Accelerometer - try keeping the phone closer to you.
This is a companion discussion topic for the original entry at https://sleep.urbandroid.org/docs/faqs/flat_graph.html