Recommended practice is to timestamp windows drivers (and software) when they are signed. Without a timestamp, the driver is not trusted after the signing cert expires, which I guess is what happened here.
With a timestamp, as long as the signing date was within the signing cert's validity period, the signed driver continues to be trusted beyond the signing certificate expiration.
With a timestamp, as long as the signing date was within the signing cert's validity period, the signed driver continues to be trusted beyond the signing certificate expiration.