Legrand Home+ Control setup error

Getting to the very last step of setting the Home+ Control integration… All the authentication seems to go smoothly until the handoff from nabucase to my local install, where i get a dialogue that says error - without any buttons or anything useful message-wise. Logs below, any help is appreciated!

Logger: aiohttp.server
Source: helpers/config_entry_oauth2_flow.py:209
First occurred: 20:35:58 (1 occurrences)
Last logged: 20:35:58

Error handling request
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/aiohttp/web_protocol.py", line 433, in _handle_request
    resp = await request_handler(request)
  File "/usr/local/lib/python3.10/site-packages/aiohttp/web_app.py", line 504, in _handle
    resp = await handler(request)
  File "/usr/local/lib/python3.10/site-packages/aiohttp/web_middlewares.py", line 117, in impl
    return await handler(request)
  File "/usr/src/homeassistant/homeassistant/components/http/security_filter.py", line 67, in security_filter_middleware
    return await handler(request)
  File "/usr/src/homeassistant/homeassistant/components/http/forwarded.py", line 100, in forwarded_middleware
    return await handler(request)
  File "/usr/src/homeassistant/homeassistant/components/http/request_context.py", line 28, in request_context_middleware
    return await handler(request)
  File "/usr/src/homeassistant/homeassistant/components/http/ban.py", line 80, in ban_middleware
    return await handler(request)
  File "/usr/src/homeassistant/homeassistant/components/http/auth.py", line 235, in auth_middleware
    return await handler(request)
  File "/usr/src/homeassistant/homeassistant/components/http/view.py", line 146, in handle
    result = await result
  File "/usr/src/homeassistant/homeassistant/components/config/config_entries.py", line 171, in get
    return await super().get(request, flow_id)
  File "/usr/src/homeassistant/homeassistant/helpers/data_entry_flow.py", line 96, in get
    result = await self._flow_mgr.async_configure(flow_id)
  File "/usr/src/homeassistant/homeassistant/data_entry_flow.py", line 271, in async_configure
    result = await self._async_handle_step(
  File "/usr/src/homeassistant/homeassistant/data_entry_flow.py", line 367, in _async_handle_step
    result: FlowResult = await getattr(flow, method)(user_input)
  File "/usr/src/homeassistant/homeassistant/helpers/config_entry_oauth2_flow.py", line 315, in async_step_creation
    token = await self.flow_impl.async_resolve_external_data(
  File "/usr/src/homeassistant/homeassistant/helpers/config_entry_oauth2_flow.py", line 172, in async_resolve_external_data
    return await self._token_request(
  File "/usr/src/homeassistant/homeassistant/helpers/config_entry_oauth2_flow.py", line 209, in _token_request
    resp.raise_for_status()
  File "/usr/local/lib/python3.10/site-packages/aiohttp/client_reqrep.py", line 1005, in raise_for_status
    raise ClientResponseError(
aiohttp.client_exceptions.ClientResponseError: 400, message='Bad Request', url=URL('https://partners-login.eliotbylegrand.com/token')

Any pointers?