Hello @Sondra123
If you move frequently during sleep, the movement can interfere with the light that bounces back to the sensors on your device.
To receive EOV data, note the following:
Look here for more information: https://help.fitbit.com/articles/en_US/Help_article/1876.htm
If the problem persist you can try restarting your Charge 4. You will not lose any of your data performing a restart. Look here to see how it’s done: https://help.fitbit.com/articles/en_US/Help_article/1186.htm
😃 Hopefully this answers your question and you will start seeing your oxygen levels being displayed again properly. Let me know if this helps