sensor.test_sensor is acting as a simple MQTT client, subscribed to the topic zigbee2mqtt/xiaomi_temp_living. The result of this test suggests that no messages are published to that topic.
Whenever one is faced with debugging an MQTT problem, I always suggest using an MQTT client (I recommend MQTT Explorer but even mosquitto_sub will do the job) to serve as an independent observer. Use the client to subscribe to the topic and examine the contents of the received messages.
I’am Back.
I downloaded the mqtt explorer and connected with hassio IP address
Then I see the esp8266 topic temp en hum
Some switches that comes from another esp8266 but no zigbee2mqtt topics
see picture
You will have to check the configuration of zigbee2mqtt because MQTT Explorer is showing that the broker located at 192.168.1.11 does not contain the topic: zigbee2mqtt/xiaomi_temp_living That explains why the state is unknown for both sensor.living_temperatur and sensor.test_sensor.
I don’t use zigbee2mqtt so I’m not qualified to answer questions about its configuration. However, according to the zigbee2mqtt’s documentation, there are several other parameters that can be used to configure it. For example, have you set a username and password on your broker? If you did, then you may need to configure zigbee2mqtt’s user and password options. Also, I don’t see a discovery option in zigbee2mqtt’s documentation. I know that’s an option in the configuration of Home Assistant’s MQTT integration.