Entities of External Triggers

Hi everyone, new to the forum

I’m having troubles with triggering external events by code in the action server, just like the EXTERNAL_dry_plant example from the documentary.

When sending out a post request like

headers = {'Content-Type': 'application/json',}
params = (('output_channel', 'latest'),)
data = '{"name": "EXTERNAL_dry_plant", "entities": {"plant": "Orchidee"}}'
requests.post('http://localhost:5005/conversations/user/trigger_intent', headers=headers,params=params, data=data)

the entity "plant" won’t be recognized by the bot and therefore the Slot won’t be set to Orchidee and stays None. Providing training data and lookups had no effect. What am I missing?