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It may not be an issue with the red light which is used during sleep so you may not see it normally.
First thing would be to shutdown and start the watch again.
Next thing is to make sure you are getting good sleep and the back of the watch is clean.
Last thing is to be patient, Oxygen Saturation may not be visible immediately after sleep, try looking later in the day. This one nightly value is calculated and it takes time to do that.
Author | ch, passion for improvement.
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