Windows Boot Manager has been blocked by the current security policy

If Windows Boot Manager has been blocked by the current security policy, reset BIOS to its default settings, check the Secure ...
Ars Technica

Unplugged system drive, PC won't boot, plugged it back in, won't boot.

Its probably just the boot order. Go into the BIOS and make sure its trying to boot from the correct hard drive first. If you aren't sure what drive you are supposed to boot from, just switch whatever ...
Börse Express

Windows 10 BIOS: Neue Leitfäden beheben Boot-Schleifen systematisch

Neue Anleitungen erklären den UEFI-Zugang, die passende Partitionierung und konkrete Reparaturbefehle für Windows-10-Startfehler.
The Windows Club

Default Boot Device Missing or Boot Failed in Windows11

Some users have reported this problem where, when they start their computer, it won’t boot. Instead, a Default Boot Device Missing or Boot Failed blue colored ...