我刚接触谷歌 Cloud ，我刚刚部署了我的第一个实例它工作正常，直到昨天，我上次使用本教程email server设置电子邮件服务器，但现在我无法连接浏览器中的ssh和谷歌 Cloud sdk in终奌站 .
网站运行正常，我不知道发生了什么请帮忙
浏览器中的错误消息
Connection Failed, and we are unable to connect VM on port 22.
终端中的错误消息
Warning: Permanently added 'xxx.xxx.xxx.xxx' (ECDSA) to the list of known hosts.
Permission denied (publickey).
ERROR: (gcloud.compute.ssh) [/usr/bin/ssh] exited with return code [255].
并且串行控制台输出它的节目
Jul 8 10:09:26 Instance sshd[10103]: error: Could not load host key:/etc/ssh/ssh_host_ed25519_key
Jul 8 10:09:27 Instance sshd[10103]: User username from 0.0.0.0 not allowed because not listed in AllowUsers
Jul 8 10:09:27 Instance sshd[10103]: input_userauth_request: invalid user username [preauth] Jul 8 10:09:27 Instance sshd[10103]: Connection closed by 0.0.0.0 [preauth] –