I am looking into this now. Hope you have followed "full integration" feature for integrating with OCUM 6.4. Please find attached document showing how to integrate OPM instance to OCUM in "Full Integration mode".
Please do not forget to "reboot" your OPM instance once you have performed the OPM integration steps in the OPM console.
With OPM2.1 and UM6.3, you can only go for partial-integration (legacy model of integrating OPM to UM). You can't use 'full-integration' until you move to UM6.4 where the reverse proxy service would honor this request and register URLs that can be routed to.