Today I am experiencing issues with vcsa vSphere we client login with my domain account i got this error  A server error Occurred 400.  To fix the issue we need to check the Appliance Time Zone. for my case i found there is  a time difference between these two appliances one is (PSC)Platform Service Controller and vCenter.    log into the PSC & vCenter below URL. So verify your ESXi host are having the correct time. and Make sure you have vCSA time-sync configured via NTP & correct the Time zone. https://clvcPSC.cloudvmkb.com:5480, https://VCENTER.cloudvmkb.com:5480.

Then restart both Appliance services.     Log in as root through an SSH.

To enable the shell :  Shell.set –enabled True 

To Launch the Shell:  shell

To Stop all services: service-control –stop –all

To start All services: service-control –start –all     

Run this command to start a specific service:  service-control –start servicename  Thank You.

Hope this will be informative for you, Thank you for Reading !