Internal Server Error UnknownError

using this api https://api.d-id.com/clips
with this json:

{
  'background': {'color': '#00ff00'},
  'config': {'result_format': 'mp4'},
  'created_by': '__some_name__',
  'driver_id': '__some_driver__',
  'name': '_some_name__',
  'presenter_id': '__some_prpesenter__',
  'script': {'input': 'this is an english text. will it work now?',
             'provider': {'type': 'afflorithmics',
                          'voice_id': '__some_voice__'},
             'ssml': False,
             'subtitles': 'true',
             'type': 'text'}}

I simply get:

{'description': 'Internal Server Error', 'kind': 'UnknownError'}

When I use an audio url it works fine, but I cannot seem so make the input text work.
Please let mw know what can I do