Windows boot camp icon greyed out
An easy fix is to power off the macOS and then hold option / alt when you power on and choose Windows.
Once you’re back in your preferred OS you can fix the boot order from the control panel.
Apple has details on most recent macOS versions here: https://support.apple.com/guide/bootcamp-control-panel/start-up-your-mac-in-windows-or-macos-bcmp29b8ac66/mac