Hello @livelife76
This help page has the recommended troubleshooting to try when you're not getting your SpO2 reading (<-- click link). SpO2 tracking uses the red & infrared sensors. However, unlike the green light heart rate sensor, these aren't easy to check to confirm that they are on.
If the recommended troubleshooting doesn't work, the next step would be to contact Support (<-- click link). Complete the prompts until you get the option to chat or call.
Rieko | N California USA MBG PE