Deploy vRealize Orchestrator, supported versions with vCD 9.1 are mentioned in below link:
Note: Orchestrator must be configured with vSphere authentication.
Make sure the vCD is registered to same vSphere (PSC) as vRO in the above step. Screenshot from lab:
Click on “+” under registration
Fill in the below details:
Click on “Up arrow” icon in Trust Anchor and upload the vRO cert (Recommend is .pem format but .cer worked in my lab)
You will see vRO successfully registered: