Windows 11 has a default feature that means it does NOT actually shutdown the operating system when you go to Start-->Power-->Shut Down. This feature is called "Fast Startup," and it is meant to get your computer going quickly when you power it on. When this setting is enabled, the restart option is how you perform a traditional power cycle.
Why is it important to know this feature exists?
Powering the computer off and on is a normal troubleshooting step and it could be that we think the computer is power cycled, but it actually is not. Without a real reboot, software does not get a proper reboot to fix itself-->such as Windows Updates, VPN software, etc.
An example of the problem:
VPN wasn't working. The FortiClient software seems to be setup correctly, but hangs when signing in. The user told us they normally shutdown the computer. It turned out that when troubleshooting the computer in person, we see the uptime as 59 days! Performing a restart did the normal power cycle and fixed the VPN issues.
See uptime in Task Manager, Performance tab.
To turn off "Fast Start," go to Control Panel.
Select Small Icons and click Power Options.
Click on Choose What The Power Buttons Do.
Click the Change Settings That Are Currently Unavailable, then you can uncheck Fast Startup.
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Technical Note. Here is the registry key for this setting. 1 means Fast Startup is enabled, 0 means it is off.