V3 API suddenly failing with both post and put requests

[RonaldA9]

I have a custom form for our patrons to subscribe to our email list, which has been working for a long time. As of today we cannot add new subscribers (post request) or update existing subscribers (put request) because we get the following error:

requests.exceptions.HTTPError: 400 Client Error: Bad Request for url: https://api.cc.email/v3/contacts

Here is the post request with names and field ids changed to protect the innocent:

{'contact_data': {'create_source': 'Contact',
'custom_fields': [{'custom_field_id': '54ab04ba-b9f2-11ed-987c-fa163eb65cb7',
'value': ''}],
'email_address': {'address': 'ronaldaaronson@hotmail.com',
'confirm_status': 'off',
'permission_to_send': 'explicit'},
'first_name': 'Ron',
'last_name': 'Aaronson',
'list_memberships': ['c175661c-b9e8-11ed-b3a8-fa163e0234d4'],
'phone_numbers': [{'kind': 'home',
'phone_number': ''},
{'kind': 'mobile',
'phone_number': ''},
{'kind': 'work',
'phone_number': ''}],
'street_addresses': [{'city': '',
'country': 'US',
'kind': 'home',
'postal_code': '',
'state': '',
'street': ''}]},
'request_type': 'post',
'url': 'https://api.cc.email/v3/contacts'}

As an image with better formatting:

Any help is appreciated!