Any chance this is the issue?
https://techcommunity.microsoft.com/blog/windows-itpro-blog/...
From TFA: "I have encountered some challenges but the most serious one is that Microsoft terminated the account I have used for years to sign Windows drivers and the bootloader."
alt Hacker News
From TFA: "I have encountered some challenges but the most serious one is that Microsoft terminated the account I have used for years to sign Windows drivers and the bootloader."