disconnected: no supported authentication methods available (server sent: publickey, gssapi-with-mic)

I had the same issue after creating a Centos 7 vm using Vagrant. In the sshd_config file it said "PasswordAuthentication no". Changing that to "PasswordAuthentication yes" and a restart of sshd solved it for me.

I had a similar issue:

• in putty console, I got the message saying "Server refused our key"
• windows error message was: "PuTTY Fatal Error" - "No supported authentication methods available (server sent: public key,gssapi-keyex,gssapi-with-mic)"

I was able to connect to EC2 via PowerShell successfully (with .pem file) so I realized that .ppk file was wrong.

Googled for about an hour and find that when you generate the .ppk with PuTTYgen for the first time you'll see the key comment filed something like "rsa-key-20191006" and what should be there is "imported-openssh-key".

After I loaded the same .pem file, as for the first time (but DID NOT CLICK on Generate) and clicked Save Private Key and used this private key for Auth, everything worked as expected.