Two of my HR92 units are displaying this on the LCD screens... one in a single-radiator zone, the other in a two-radiator zone. I am not being reported any issues on the controller unit but neither of those rooms seems to be working.

Does it mean these have somehow got unlinked and need to be re-paired? I assumed Google would give me an obvious answer but I couldn't see one. Is there a page that lists all the possible messages the units can show?

By the way I also realised when checking everything I cannot tell which HR92 is the master in a 2-radiator zone. Is there supposed to be a little icon or do I just have to remember? I want to make sure the radiator with best airflow is the one being used as thermostat.
Thanks.