QAuthenticator5 NTLMv2 not working in HTTPS

[port]

QAuthenticator NTLMv2 with HTTPS is not working for me, while it works fine with HTTP (IIS 10)

we followed [NTLMv2 authentication in Qt] https://stackoverflow.com/questions/14706851/ntlmv2-authentication-in-qt

by doing

authenticator.setUser("")
so the credential of current logged-in user is sent to server (HTTP works fine, but not HTTPS)

does anyone know a fix/workaround ?

also posted in
https://stackoverflow.com/questions/55952622/qauthenticator-ntlmv2-with-https-not-working