Well...serveral things to check:
a) did you actually connect vRO to vCenter. Meaning did you run the appropriate workflows in vRO
b) if you are using vRO with vRA and you activaed vRA Authentication. You will have problems working with vCenter as it uses SSO and not vIDM
c) Did you allow the user that currently is loged into vCenter access to vRO?
d) Did you check if vCenter actually can reach vRO via ping on port 443?
Error sound like a timeout so I guess its a) or d)
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VRealize Orchestrator Cookbokk 2nd Edition
VMware vRealize Orchestrator Cookbook - Second Edition | PACKT Books