SSH connection time out, error 4003 failed to connect to backend
-- Connection via Cloud Identity-Aware Proxy Failed
-- Code: 4003
-- Reason: failed to connect to backend
Please check official documentation on Failed to connect to backend from troubleshooting SSH.
These errors occur when you try to use SSH to connect to a VM that doesn't have a public IP address and for which you haven't configured Identity-Aware Proxy on port 22.
To resolve this issue Create a firewall rule on port 22 that allows ingress traffic from Identity-Aware Proxy.