No support authentication

I'm trying to use a cert to login with.

PuTTY has no trouble connecting to this server.
I add the same private key and winscp can login.

I try another server with the same private key and it works.
but on this server, I keep getting this error.

Disconnected: No support authentication methods available (server sent: publickey,gsspi-keyex.gssapi-with-mic)
Using username "root"

Authentication failed.

Where do I find the authentication log?

Posi211 wrote:

I try another server with the same private key and it works.
but on this server, I keep getting this error.

What do you mean by "server with the same private key" and "it works"?

Where do I find the authentication log?

See https://winscp.net/eng/docs/ui_pref_logging