The message "For your security, some settings are managed by your system administrator" typically appears when the settings for BitLocker Drive Encryption have been configured or restricted by a system administrator using Group Policy.
This means that the specific settings you're trying to access are locked and can only be modified by someone with the appropriate permissions, such as a system administrator.
As a workaround, you can try to check the local group policy editor by running the "gpedit.msc" command in the Run dialogue box. Then navigate to Computer Configuration > Administrative Templates > Windows Components > BitLocker Drive Encryption. Here you can check the settings that are applied and if there is any restriction on the settings you are trying to access.