Hi Tutu7733,
To use Screen Time across your devices, we recommend that you try the steps here: Keep track of your screen time on iPhone - Apple Support
To perform the recommended troubleshooting steps via the link above, complete the steps in the section titled "Use Screen Time on all your devices."
To share your Screen Time settings and reports across all your devices, make sure you’re signed in with the same Apple ID on each device and Share Across Devices is turned on.
1. Go to Settings > Screen Time.
2. Scroll down, then turn on Share Across Devices.
We recommend the steps above because they will show you how to share your Screen Time settings and reports across all your devices.
Also, to se up Screen Time for a family member, follow the steps below.
Screen Time allows you to manage settings for downtime, app use, contacts, content ratings, and more. To use Screen Time, your child must be using an eligible device. See the Screen Time section in the Apple Support article System Requirements for iCloud.
1. Go to Settings > [your name] > Family Sharing > Screen Time.
2. Tap the child you want to set up Screen Time for.
3. Tap Screen Time, then follow the onscreen instructions.
4. For information about Screen Time settings, see Set up Screen Time for a family member on iPhone.
5. To learn more about the different content & privacy restrictions, see the Apple Support article Use parental controls on your child’s iPhone, iPad, and iPod touch.
If your child requests more screen time, you can approve or decline the request in Settings > Screen Time or in Messages .
Please let us know the outcome after giving the above steps a try.
Thanks for using the Apple Support Communities.
Cheers!