vCenter Server 5.5 uses SSL certificates to secure communication between the server and its clients. These certificates have a limited lifespan, typically one year, and must be renewed or replaced periodically. When the certificate expires, the vCenter Server will no longer be able to establish secure connections with its clients, causing a range of issues.
Identify whether the Machine SSL or SSO certificate is the culprit. Replace the expired certificates and restart services. vcenter server 5.5 certificate expired
Before attempting a fix, you must confirm that expiration is the root cause. vCenter Server 5
have their own certificate stores. If these are expired, you'll see "Failed to connect" errors even after fixing the main vCenter service. You may need to use the SSO Certificate Tool provided by VMware (Broadcom) to update these components. Summary Checklist Backup your vCenter Server (Snapshot or VM backup). Identify whether the Machine SSL or SSO certificate
"C:\Program Files\VMware\Infrastructure\SSOServer\ssolscli.cmd" manage-secrets -a reset-all