FYI: Smartscreen kicks in, because even though the certificate may have been valid

[exoosh]

... it no longer is and you forgot to timestamp the signature. Without timestamp and in the absence of the EKU for "lifetime signing" (which means that a signature expires along with the certificate), this means the .exe is no longer deemed as validly signed.

With best regards,

an alumni of your Windows Internals course (2021) ;)