vSphere web Client says 500 SSO Error Null after reboot of vCenter Virtual Appliance.
Once you are connected to your vCenter Server Appliance
check your log file hostname# cat /var/log/vmware/vsphere-client/logs/vsphere-client-virgo.log
Reading the logs – The PSC and the VCSA time was off by 20 minutes.
I configured the NTP and rebooted the vcsa and the psc and the web client came back to normal.