You need to ensure your personal SSH key works on every instance in your project.

Overview By creating and managing SSH keys, you can let users access a Linux instance through third-party tools. An SSH key consists of the following files: A public SSH key file that is applied to instance-level metadata or project-wide metadata. A private SSH key file that the user stores on their local devices. If a user presents their private SSH key, they can use a third-party tool to connect to any instance that is configured with the matching public SSH key file, even if they aren't a member of your Google Cloud project. Therefore, you can control which instances a user can access by changing the public SSH key metadata for one or more instances. https://cloud.google.com/compute/docs/instances/adding-removing-ssh-keys#addkey