According to the TAG, the Windows client expects the key to be in PuTTY's special format. If it isn't, and one tries to connect using PKA, the client gives the message: "Server does not support public key authentication." The server does support PKA; the key is just in the wrong format. A message more along these lines would be much more helpful.
*** Bug 4249 has been marked as a duplicate of this bug. ***
(In reply to Aaron Sowry from comment #0) > According to the TAG, the Windows client expects the key to be in PuTTY's > special format. Note that this is no longer true, our TAG now says: > The client currently only supports the OpenSSH key format. If your keys > are in another format, e.g. for PuTTY, then they must first be converted > before they can be used with ThinLinc. https://www.cendio.com/resources/docs/tag-devel/html/authentication_publickey.html?highlight=putty#client-configuration
*** This bug has been marked as a duplicate of bug 7313 ***