In a multi-instance cluster, one specific node can be accessed without issue, but accessing it through other nodes displays an HTTP 596 error (`tls_process_server_certificate: certificate verify failed (596)`). Online solutions are ineffective, and updating the certificate does not resolve the issue.

Problem Confirmation

By checking `/etc/pve/.members`, you can find that the IP address corresponding to the problematic node is incorrect. Directly connecting to the faulty node’s web UI and viewing the certificate information reveals that the alternate name in the `pve-ssl.pem` certificate of the faulty node contains an incorrect IP address.

Solution

1. Correct the IP address in the hosts file of the problematic node: `/etc/hosts`.

2. Restart the cluster service: `systemctl restart pve-cluster`.