I have a self-written kernel driver, which has a digital signature DigiCert Sha2 High Accuracy Code Signing CA, certificate is valid from 21.04.16 till 24.05.2017.

As I understand Driving signing changes in Windows 10, this driver should not work on my Win 10 1607 computer, because it is not assigned by Microsoft, but it still works. Otherwise, on the PC of my colleague we receive the message "Windows requires a digitally signed driver..." and the message "Failed to load device driver" after that.

On both computers sequre boot is on and systems were not upgraded from previous OS, it was always Win 10 1607.

Why can this happen?