I have 40 Carrier units with Native BACnetIP communication protocol. Each controller has 840+ objects. I can discover the device and objects on the local subnet, however, it takes over a minute for the objects to populate in my discovery tool (InneaBACnetExplorerFree). In Ignition, I have configured the IP address, UDP, Remote Device Number, and BBMD to connect to the device. I have checked, and unchecked COV, with no connection. Not sure what the next step would be.
I would recommend changing the logging level for the BACnet driver to see if there are any errors that come up. Wireshark was useful when diagnosing my BACnet issues as well. It seems like the driver can be a little flaky with different BACnet units - I have a Schneider AS-P that I just can't pull data from.
Another option is to try Kepware's BACnet driver.