Bigin to Mailchimp using Zoho Flow

Bigin to Mailchimp using Zoho Flow

I am trying to make a basic connection to Mailchimp from Bigin by Zoho. The connection is "Contact Created" > "Add or update subscriber". All connections are working fine between Bigin > Zoho Flow and Zoho Flow > Mailchimp.

I thought it was because some fields and null/empty, however these are not "required" fields in Mailchimp, so should not matter that they are empty/null.

The error is: Mailchimp says "The resource submitted could not be validated. For field-specific details, see the 'errors' array."

However no "'errors' array" is provided?

Here is an example of the code submitted to Mailchimp from Bigin (with personal details removed):

{
"Address address line 1": "",
"Company": {
"name": "Company Name Ltd",
"id": 319998000000279668
},
"Address address line 2": "",
"Subscriber Status": "subscribed",
"First Name": "Firstname",
"Subscriber email": "name@company-name.co.uk",
"Address state": "",
"Contact Type": "Prospect",
"Birthday": "",
"Address zip": "",
"List": "935cf1cba2",
"Address city": "",
"Address country": "United Kingdom",
"Last Name": "Lastname",
"Phone Number": "",
"Tags": ""
}