Hi,
I'm confused a bit. It appears you are trying to use both vCO 5.5.2 and vRO 6.0.3 with VC 5.5.2 but the plug-ins are different (they have different deployment mechanism, different extensions in MOB, etc.). I'd recommend to stick to the version of vCO that you got installed together with VC - in this case, 5.5.2.
Then, check the following:
- Verify that vCO is configured with SSO authentication, and that it is the same SSO instance used by VC/Web Client
- Verify that vCenter instance is added correctly to vCO and that there is a 5.5.x-style extension in the MOB. Its name is com.vmware.orchestrator.[some-guid]
- Verify that the extension's server property contains a record with URL property pointing to the correct vCO server - https:[vco-ip]:8281
- Verify that the user you are using to connect to Web Client has correct permission; eg. you should be able to login to vCO Java Client with this user
If all of the above is valid, check Web Client log file (vsphere_client_virgo.log) for any errors related to loading of vCO plugin and connecting to vRO server.