Upgrading Putty to 0.78 (the last version) solved the issue.
Thanks @sspencerwire, I followed your link, and lead me to another link where I found the solution.
I found the solution on openssh - SSH server gives "userauth_pubkey: key type ssh-rsa not in PubkeyAcceptedAlgorithms [preauth]" when connecting with Putty - Unix & Linux Stack Exchange
Thanks very much, @sspencerwire and @jlehtone for your great help