Add user error

I want to add a user and get a “unknown error” in the GUI. The log says

Logger: homeassistant.components.websocket_api.http.connection
Source: auth/providers/homeassistant.py:44
Integration: Home Assistant WebSocket API (documentation, issues)
First occurred: 11:01:49 (1 occurrences)
Last logged: 11:01:49

[140563195422176] Error handling message: Unknown error
Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/components/websocket_api/decorators.py", line 25, in _handle_async_response
    await func(hass, connection, msg)
  File "/usr/src/homeassistant/homeassistant/components/config/auth_provider_homeassistant.py", line 33, in websocket_create
    provider = auth_ha.async_get_provider(hass)
  File "/usr/src/homeassistant/homeassistant/auth/providers/homeassistant.py", line 44, in async_get_provider
    raise RuntimeError("Provider not found")
RuntimeError: Provider not found

My HA runs in a docker. Any ideas?