Permission denied (publickey).

The SSH client was unable to authenticate with the server because it could not find a valid public key. This typically happens when the public key is not added to the server's authorized keys or the private key is not accessible.

This broke because the SSH server requires a valid public key for authentication, and either the key is missing, incorrectly configured, or the permissions on the key files are not set correctly.

To fix this, ensure that your public key is added to the server's `~/.ssh/authorized_keys` file. Also, check that your private key has the correct permissions (should be readable only by you) and that you are using the correct key when connecting.