Integrate with MailChimp

Hi,

I have found a lot of articles looking to integrate Wix forms with MailChimp using wix-fetch, particularly @Toby's post. However, although I followed the other resources exactly, it is not working for me. Here is my code.

Backend:

import {fetch} from 'wix-fetch';
import {getSecret} from 'wix-secrets-backend'

const API_KEY_64 = getSecret('MailChimp');
const LIST_ID = "d4b50956ba";

export function sendToMailChimp(data) { 
    fetch("https://us6.api.mailchimp.com/3.0/lists/" + LIST_ID + "/members", {
        method: 'POST',
        headers: {
            'Authorization' : 'apikey ' + API_KEY_64,
            'Content-Type' : 'application/json'
        },
        body: data
    })
    .catch(err => console.log('ugh'));
}

// Execute the sample function above by copying the following into your page code

Frontend:

import {sendToMailChimp} from 'backend/mailChimp.jsw'

export function getSubscribers1_wixFormSubmitted(fields) {
    console.log('hook 2.0')
    let lastName
    let email = fields.fields[2].fieldValue
    let firstName = fields.fields[0].fieldValue
    
    if(fields.fields[1].fieldValue !== '') {lastName = fields[1].fieldValue}
    else {lastName = ' '}

    if(typeof email === 'string' && typeof firstName === 'string') {
    
    var data = {
        "email_address":email,
        "merge_fields": {
            "FNAME":firstName
        },
        "status":"subscribed"
    };

    
    // Stringify into JSON format
    let stringData = JSON.stringify(data);
    
    // Process request
    console.log(data)
    console.log(stringData)
    sendToMailChimp(stringData);
    }
    return data;
    
}

Everything in the front end code is working great. My console.log results get me:

{"email_address":"a@a.com","merge_fields":{"FNAME":"A"},"status":"subscribed"}

Which is exactly what I am looking for. However, it is not translating to MailChimp.

Any help greatly appreciated! Thanks.