Breathing Variations doesn't work F7pro 21.19

After the update the new function worked only one night. In the following nights I get the message that: no data... to get data keep the heart rate option turned on during sleep.

 According to the instructions, I turned on the pulse oximeter for the night. However, I go to sleep later than the sleep schedule.

Could that be the reason for the issue?

All other sleep data, including oxygen saturation, is in the sleep report.