During a Partner enablement session we figured out that a new deployed vRealize Operations Manager (vROPS) instance was not able to be started correctly. Login into https://vrops.fqdn/admin the following was shown under system status.
A server error occured  or vCenter Server ‘once upon a time’
After fixing a failed SSD of one of my lab-hosts I had some minor issues with my vCenter. Whenever I logged on into it I received this error.
“ An error occured while sending an authentication request to the vCenter Single Sign-On server – An error occured when processing the metadate during vCenter Single Sign-On setup – null.”
fair enough I checked the :5480 VAMI of my PSC and vCenter and the vCenter showed me the SSO was not initialized.