The boiler has lost contact with the room controller for the second heating zone, so that zone may not heat properly, but the boiler itself is likely still working safely.

DIY fix possible

Check the batteries in the wireless room thermostat or room unit for heating circuit 2, and replace them if they are low.Make sure the room unit is not blocked by furniture or curtains, and is not in direct sunlight or near a heat source.Switch the boiler off at its on/off switch for 2 minutes, then switch it back on and check whether the fault clears.If the code returns, book a Viessmann-approved heating engineer to check the room unit wiring and connections, and to replace the sensor if needed.