It appears Cygwin SSHD's functionality is partially broke in the later versions, where SSHD runs as SYSTEM (no longer cyg_server).
On reboot, any attempt to SSH into the server *before* any previous logon attempt (RDP/locally/etc) is quickly denied: debug1: Offering public key: /home/<user>/.ssh/id_rsa debug3: send_pubkey_test debug2: we sent a publickey packet, wait for reply Connection closed by <server_addr> Once an RDP/local login is attempted, regardless of success/failure, subsequent ssh attempts will progress to the password prompt which eventually gets us in. The Event Viewer shows the attached error message, relating to a NULL SID and 0xC00000BB status. ssh_as_first_login.txt <http://cygwin.1069669.n5.nabble.com/file/t11987/ssh_as_first_login.txt> It was a rather vanilla 'ssh-host-config' run to get it installed: strict modes = no, no special ssh_/sshd_config settings at this point. Running latest cygwin packages on Windows Server 2016 Standard: CYGWIN_NT-10.0 <server_name> 3.1.4(0.340/5/3) 2020-02-19 08:49 x86_64 Cygwin ... openssh 8.2p1-1 OK -- Sent from: http://cygwin.1069669.n5.nabble.com/Cygwin-list-f3.html -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple