Haverland Radiators Smart Box Integration

Hoping someone can help me, I’m getting a 401 error as many have in here but reading through I’ve not really seen a solution, not at least one that works for me.

401 Client Error: Unauthorized for url: https://api-haverland.helki.com/client/token

As far as I can tell my details are correct, I used Postman to manually connect to the API using my details and that works fine. Below is my configuration, obfuscated slightly for obvious reasons.

smartbox:
  accounts:
  - api_name: api-haverland
    username: [email protected]
    password: xxxxxxxxxxxx
    device_ids:
    - ee0aee5e211040cbe2
  basic_auth_creds: NTxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxaQ==

Any idea what it might be, or ways I can work out whats going on? Running for debug logging and it really is no help at all…