John is getting a message asking for his BitLocker key. He's never turned it on. Leo says that BitLocker is a Windows encryption app, and it uses certificates to unlock and lock it. It sounds like John may have turned it on during setup without realizing it. If he didn't make a backup copy of the certificate, and he loses it, he may be in trouble. But it does offer to save the certificate to a Microsoft account, so look there to see if the cert is there. Search for BitLocker Recovery Keys. If it's not there, then John may be out of luck and will have to format his drive, reinstall Windows 10 and start over.