Battery health, not showing

If an app or feature on your device is not working or is restricted, it may have been disabled using Screen Time, or by an IT administrator if you are using a device owned by an employer or educational institution. See how to use Screen Time on an iPhone, iPad, or iPod touch by clicking here --> Use Screen Time on your iPhone, iPad, or iPod touch - Apple Support

Well, you have already marked your issue as solved and answered, so you may not need to read this post.

Have you tried a Forced Restart? Force restart iPhone - Apple SupportAppleOfficial Apple Support › guide › iphone › ios

Follow the instructions very carefully.

Is it possible that you have replaced the battery in the phone recently? Battery Health will not display if the wrong type of battery has been installed on your phone.