Receiving the message in subject line, when I attempt to boot from an external drive or DVD. Both of which were bootable before. EFI boot order Options & BIOS settings seems normal when viewed from F9 & F10 manipulations. F2 testings on HD shows everthin as OK..
There was a new HD installed with a clean Windows 10 installation too.
Perhaps there might be something that I am overlooking or forgot, any suggestions?