HI Sathish,
Check if the ESX(i) certificate is not expired (In a Browser enter the IP of ESXi and Validate the Certificate).
If you see a Expired certificate then follow below steps.
1. Backup Your existing Certificates (Backup Folder /etc/vmware/ssl)
2. Run below command in ESXi shell.
/sbin/generate-certificates
3. Reconnect from vCenter.
Let me know how it goes, All the best.
Karthic.
vRNI TPM