Hi,
The 'No Sync' usually indicates that they aren't receiving messages from the controller. If you haven't made any recent changes to your set-up, I'd try moving the controller into the same location as the HR92s and it should disappear within about 5min. It sounds like something is interfering with the signal, but if you're not seeing any error on the controller then it's likely that some messages are getting through in the direction HR92 -> controller. Try some alternate locations for the controller which might fix it if there isn't anything obvious which might be blocking the signal.
To quickly find out which HR92 is the temperature sensor in a zone with more than 1 radiator, I suggest removing one of the HR92s plus adapter & placing it in a warmer/cooler location and see if the temperature changes. If not, then it's just an actuator.
Dan