I'm facing the problem, that SSH works using a public/private key, but not SFTP via FileZilla. The key is added to FileZilla. When I do try to connect, it says:
FATAL ERROR: No supported authentication methods available (server sent: publickey)
I set PasswordAuth to no in the ssh config. I also restarted both my PC and the server. I hope you can help :)
Also, I recently installed Ubuntu 18.04 on an old machine with the same settings, SFTP works there.