I can not connect or ssh to datalab machine

[OrielResearchCure]

Hello,

I have created a machine few days ago. At some point today, I was not able to connect to it or ssh.

trying to connect with verbosity debug, I get the following messages:

DEBUG: (gcloud.compute.ssh) [/usr/bin/ssh] exited with return code [255]. Traceback (most recent call last): File "/google/google-cloud-sdk/lib/googlecloudsdk/calliope/cli.py", line 983, in Execute resources = calliope_command.Run(cli=self, args=args) File "/google/google-cloud-sdk/lib/googlecloudsdk/calliope/backend.py", line 807, in Run resources = command_instance.Run(args) File "/google/google-cloud-sdk/lib/surface/compute/ssh.py", line 266, in Run return_code = cmd.Run(ssh_helper.env, force_connect=True) File "/google/google-cloud-sdk/lib/googlecloudsdk/command_lib/util/ssh/ssh.py", line 1269, in Run raise CommandError(args[0], return_code=status) CommandError: [/usr/bin/ssh] exited with return code [255].
any idea how to resolve this.

Thanks,
eilalan