Hi luqmanalkassim,
Welcome to Apple Support Communities. We understand that you're having an issue with using the Blood Oxygen app. We'd like to help.
Since this app is available in your current region, we'd like to isolate this issue to see if we can get to the bottom of this. Do you notice this issue on both cellular and Wi-Fi? Are you using a VPN to access the internet? If so, that can change your location and may be the cause of this issue.
If you're not, make sure you meet all these requirements:
How to use the Blood Oxygen app
Make sure that you meet the below requirements and follow the steps to set up the Blood Oxygen app.
Here's what you need
* Make sure that the Blood Oxygen app is available in your country or region. You will be able to see this during the setup process.
* Update your iPhone 6s or later to the latest version of iOS.
* Update your Apple Watch Series 6, or Series 7, Series 8, or Ultra to the latest version of watchOS.*
* The Blood Oxygen app is not available for use by people under 18 years old. You can confirm or set up your age in your Health Profile.
Then, check out these steps to make sure everything is set up correctly: How to use the Blood Oxygen app on Apple Watch - Apple Support
If you need additional help with this, we recommend that you reach out to Apple Support for this issue. This link will help you get that conversation started: Get Support: Apple Watch
Hope that helps!