Dead KC868-H32B ?

[bigramon]

if you can send command manually, board is working. now need to confirm, which stage have problem . mqtt broker or HA. do you install mqtt broker with home assistant in same server?

The problem is clearly located in the implementation of the Kincony MQTT implementation, neither in HA nor in the mosquitto broker which are both products widely used in the home automation world.
Moreover:
1/ I have 109 devices connected to my mqtt broker and 1 of them is having an issue: the kc868-h32b
2/ when manually entering mqtt commands from mqtt explorer, I see the commands being sent to the broker but the kc868 does not take them into account => broker is working fine but the kc868 no longer listen to the mqtt broker commands
3/ HA and the mosquitto broker run in separated and dedicated docker instances - no cpu nor memory issues + see point 1/