Okay, after a lengthy chat session with DJI support, I still haven't yet successfully been able to confirm that the RID is being transmitted. But here are some tips:
-- The RID serial must be registered with the FAA before it can be transmitted by the drone. I'm not sure how that works but apparently you must register the RID for everything to work.
-- The RID is only transmitted while the motors on the drone are running.
-- Once registered and with motors running, the RID should be visible by scanning (on a phone or whatever) available wifi networks. This hasn't worked for me yet, but DJI did tell me that there may be a delay after registering the RID, so I'm going to leave it a while then try again. Supposedly you can find RID status in the Go 4 app also, but I wasn't able to figure out how to do that.