Extract string from mqtt json

[upbeat gull]

Hi everybody,
i am trying to extract a json string that comes via mqtt to HA.
This is what mqtt explorer receives:

{
"header": {
"source": "dialogsystem",
"type": "intent",
"type": "event",
"version": "1.6.0"
},
"content": {
"orthography": "schalte das Licht im Wohnzimmer ein",
"intent": "switch_light",
"slots": [
{
"name": "light_device",
"value": "Licht",
"orthography": "Licht",
"ids": [
"0x0000000000000001"
]
},
{
"name": "room",
"value": "Wohnzimmer",
"orthography": "Wohnzimmer",
"ids": [
"0x000000000000000C"
]
},
{
"name": "light_target_state",
"value": "ein",
"orthography": "ein",
"ids": [
"0x0000000000000001"
]
}
]
"name": "playing",
"value": false
}
}

My mqtt sensor looks like this:

mqtt:
sensor:
- name: "Content Orthography"
state_topic: "speech/output"
value_template: "{{ value_json.content.orthography }}"

I can see the defined entity but no values and no changes.

Any help would be appreciated.

[dense sundial]

What do you get when you subscribe to the topic in HA?

-> Integrations -> MQTT -> Configure

[upbeat gull]

When i subscribe to the topic in HA the result is the same:

Nachricht 16 empfangen auf /speech/output um 10:45:
{
"header": {
"source": "dialogsystem",
"type": "intent",
"version": "1.6.0"
},
"content": {
"orthography": "schalte das Licht im Wohnzimmer ein",
"intent": "switch_light",
"slots": [
{
"name": "light_device",
"value": "Licht",
"orthography": "Licht",
"ids": [
"0x0000000000000001"
]
},
{
"name": "room",
"value": "Wohnzimmer",
"orthography": "Wohnzimmer",
"ids": [
"0x000000000000000C"
]
},
{
"name": "light_target_state",
"value": "ein",
"orthography": "ein",
"ids": [
"0x0000000000000001"
]
}
]
}
}
QoS: 0 - Retain: false