Hi,
Many users have recently reported this issue, and based on feedback, the usual troubleshooting steps do not seem to resolve it.
This looks like a temporary glitch on Microsoft’s side, possibly due to a high number of users trying to switch out of S Mode at the same time. In most cases, waiting 24–48 hours allows the system to stabilize and the issue to resolve automatically.
If the issue is urgent and you still cannot switch out of S Mode, the alternative option is to perform a clean installation of Windows. If you choose to proceed, please make sure to back up all your important files first before continuing.
For a step-by-step guide with illustrations, click the link below and scroll down to the 'Steps to reinstall Windows with media' section, then expand the 'Clean install' option:
https://support.microsoft.com/windows/reinstall-windows-with-the-installation-media-d8369486-3e33-7d9c-dccc-859e2b022fc7