Hi @Topaz,
I’m not quite sure that I understand your question (maybe because I don’t use HA), but are you saying that you succeeded in writing a value to 0x42F1? Based on the discussion on the Contribution: Samsung ASHP NASA link <-> MQTT bridge (Home Assistant) thread, I had been under the impression that the only Message Addresses we could write to were those associated with FSVs (like the 0x40A7 you mention for #5051). Personally I use SNET-Pro2 v1.14.3 to reset my FSVs (on my laptop), as the packet syntax for outgoing messages is a bit daunting (all those 0x55555555555s…)