To resolve this issue follow the solutions below as per the scenario.
Note: if you receive a new tab with a lot of text by clicking on Download trusted root CA, open the same link on a different browser or do a right-click and select the option Save as...
Notes:
In some cases the Serenity database becomes corrupt, reset Serenity DB to resolve the issue.
The impact of resetting the Serenity database is very tiny -- when you next connect to the vCenter through the web client, it will take a few seconds longer than usual while the system rebuilds that database.
Follow the below steps:
# service vsphere-client stop
rm -rf /etc/vmware-vsphere-client/SerenityDB/serenity/*
# service vsphere-client start