Sleep data may not be recorded in the following three cases.

1. Sleep is recorded only between 20:30 and 11:00 the next day, so sleep outside this window is not saved.
2. If the ring’s battery runs out or is low during sleep, records may be missed.
3. If data sync with the app is not complete, sleep records may not be reflected.

If the problem continues even when none of these apply, reset the ring and reconnect. (Reset: My Page > Smart Ring Settings > Device Reset)