Unable to load key

The error you're encountering suggests there's an issue with the SSH key configuration on your Lightsail Debian instance. This problem can occur after system updates, particularly when upgrading to newer versions of Ubuntu or Debian.

To resolve this issue, you can try the following steps:

1. First, attempt to connect using a third-party SSH client like PuTTY, as suggested in the error message. This might work if the issue is specific to the Lightsail browser-based SSH.

2. If that doesn't work, you may need to update the SSH configuration on your instance. However, since you can't access the instance directly, you'll need to use an alternative method:

   • Create a snapshot of your current instance.
   • Launch a new instance from this snapshot.
   • During the launch process, you can add a startup script to modify the SSH configuration.

3. In the startup script, you can add the following lines to the SSH configuration file (/etc/ssh/sshd_config):

   TrustedUserCAKeys /etc/ssh/lightsail_instance_ca.pub CASignatureAlgorithms +ssh-rsa

4. If you're still unable to connect, you might need to use the Lightsail console to reset your instance's password or SSH key.

5. As a last resort, if none of the above steps work, you may need to contact AWS Support for further assistance.

Remember to review and update your security configurations once you regain access to prevent future issues while maintaining proper security practices. Sources
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