Its a new installation of putty (on a new installation of windows 10). There is nothing on registri about SshHostKeys
And no saved session, I guess. (Sorry, I read @grahamh’s post as being from you.)
As I say, it could be a Win10 issue. I’m not really much of a Putty expert.
There is another SSH client you could try, from Bitvise: Bitvise SSH Client Download | Bitvise
What version of OSMC are you on?
Did you modify sshd config?
There’s something strange either with your Win10 box or OSMC configuration. I was able to install Bitvice SSH client and connect first time:
22:40:52.622 Current date: 2017-08-31
22:40:52.622 Bitvise SSH Client 7.34, a fully featured SSH client for Windows.
Copyright (C) 2000-2017 by Bitvise Limited.
22:40:52.622 Visit www.bitvise.com for latest information about our SSH software.
22:40:52.622 Run 'BvSsh -help' to learn about supported command-line parameters.
22:40:52.622 Cryptographic provider: Windows CNG (x86) with additions
22:40:54.007 Loading default profile.
22:40:54.007 Loading default profile failed: RegOpenKeyExW() failed: Windows error 2: The system cannot find the file specified.
22:40:54.007 Loading a blank profile.
22:41:39.073 Started a new SSH2 session.
22:41:39.104 Connecting to SSH2 server 192.168.8.33:22.
22:41:39.354 Connection established.
22:41:39.775 Server version: SSH-2.0-OpenSSH_6.7p1 Debian-5+deb8u3
22:41:39.791 First key exchange started. Cryptographic provider: Windows CNG (x86) with additions
22:41:40.555 Received host key from the server. Algorithm: Ed25519, size: 256 bits, MD5 fingerprint: <snip>, Bubble-Babble: xidep-gusan-zavoc-nuzek-tymin-nupar-nolyr-dubah-cyhez-rifir-nuxix, SHA-256 fingerprint: <snip>
22:41:43.301 Host key has been saved to the global database.
22:41:43.348 First key exchange completed using diffie-hellman-group14-sha1. Session encryption and integrity: aes256-gcm, compression: none.
22:41:43.628 Attempting password authentication.
22:41:44.003 Authentication completed.
22:41:44.330 Terminal channel opened.
22:41:44.330 SFTP channel opened.
22:41:57.871 SFTP channel closed by user.
Unfortunately, I can offer no other ideas.