Thanks for clarification.
Could you also check if the FQDN you used to register vCenter in vRO and FQDN of the vCenter visible in Web Client are spelled exactly the same? Note that casing matters; eg. myVcenter.domain.com is not equivalent to myvcenter.domain.com (the former name contains uppercase V and the latter has a lowercase v).
BTW, we had few error reports with exactly the same symptoms, and in all cases it was because of different spelling of the FQDN ![]()