You will have to configure Secure TCP (TCPS) for Oracle VM Manager (Doc ID 1456338.1)
Your OVMM is listening on port localhost.localdomain:54321 it should be listening on *.54321.
The only way to get it working is to configure a secure TCPS. This will allow your OVMM to listen on *.54322
Remember when you add the OVMM asset select port 54322 and TCPS.
Thanks 894351. Your reference to the doc above fixed my issue of getting OVM 3.1.1 discovered by Ops Center 12c:
Using Bundled Scripts
When you perform a fresh install of Oracle VM Manager 3.1.1, scripts are provided under /u01/app/oracle/ovm-manager-3/bin of the Oracle VM Manager server
•secureOvmmTcpGenKeyStore.sh: create the keystore
•secureOvmmTcp.sh: use the generated keystore to enable the TCPS service for Oracle VM Manager