I didn't find this info online and had to figure it out myself, so I thought I'd share.

I own a stationary bike, the "Spinner Chrono Power" and had been bummed to only record heartrate on my sessions. Then I finally looked into the features and learned it has ANT and so does my FR255!

But when I connected my watch to the bike, I wasn't getting heartrate readings anymore. I saw the heartrate sensor running, but no heartrate displayed on the watch or recorded in the workout.

Eventually I tried broadcasting my heartrate to the bike, and that was the fix. I guess when the watch is connected to the bike, it only uses the bike's data. So I have to broadcast my watch heartrate to the bike, and have the bike send the heartrate back to the watch.

It's pretty silly but I'm glad to have it working.