Dear customer.
Welcome to Microsoft Community.
In your description, it seems that your computer is still on after you clicked Shutdown.
I noticed that you have tried to adjust the power management, turn off the fast startup, change the registry, and even check the BIOS. Thank you for your efforts and attempts to solve this problem, and I understand that the current situation has caused you a lot of trouble and frustration.
Are you using any third party software that runs in the background? Some software may prevent the computer from shutting down completely.
To determine this possibility, I recommend trying a clean boot which starts Windows with a minimal set of drivers and startup programs. It can be used to determine whether a background service or program is interfering or causing a problem.
These steps of "clean boot" might look complicated at first glance. However, to avoid any trouble for you, please follow them in order and step-by-step.
In clean boot, try clicking shutdown to see if the same problem occurs, which can rule out third-party software in this regard.
You can also do some checking in the Device Manager
1 Right-click on the Start button and select Device Manager
2 Find System devices, then find Intel(R) Management Engine interface
3 Right-click and select Properties
4 Check to see if there is a power management tab, and if so, try changing the state of “Allow the computer to turn off this device to save power” to see if enabling or disabling it improves your problem.
BIOS settings may also have an impact. Even if you have checked for BIOS updates, we recommend that you try to reset the BIOS settings as instructed by the motherboard manufacturer or the motherboard manual.
Disclaimer: Microsoft provides no assurances and/or warranties, implied or otherwise, and is not responsible for the information you receive from the third-party linked sites or any support related to technology.
If you are going to modify BIOS Settings, please back up all your personal files first to ensure you do not lose data.
See if the same problem exists after resetting the BIOS.
In the meantime, you can also try to shut down your computer using commands.
1 Search for “Command Prompt” on the taskbar, right-click it, and select Run as administrator.
2 Type in the following command and press the Enter key
shutdown /s /f /t 0
3 Check if the same problem exists after using this command.
The above methods are not the final solution, they are more like a check for you on this issue, please let us know the results after you try them, they will help to narrow down the cause of the problem and we will determine the problem for you based on your results and provide further assistance.
It's my honor to provide you with some advice and I hope my efforts can bring you some convenience.
Thank you for your understanding and support.
Best regards,
Zev - MSFT | Microsoft Community Support Specialist