Unable to see vCO in vSphere Web Client

I'm currently using vRealize Orchestrator 6.0.0. I've been trying to add the extention to my vSphere Web Client but it still does not work.

I configured the SSO Authentication, the network, imported the SSO Certificate. I ran both workflows "Add a vCenter Server instance" and "Register vCetner Orchestrator as a vCenter Server extension" in "Library / vCenter / Configuration".

When I try to restart my vSphere Web Client service, I can see the vCO in it, but it disappear after a minute. And I can the see the error message "

Could not connect to one or more vCenter Server systems:

https://{vCenterIP}:443/sdk"