Ebay API – Error ID 2004 when selling an item using Ebay API with Python

I am trying to use the eBay API to sell an item with python however, I keep on getting this error
{"errors":[{"errorId":2004,"domain":"ACCESS","category":"REQUEST","message":"Invalid request","longMessage":"The request has errors. For help, see the documentation for this API."}]}

I have no idea why it is giving me this and have googled with nothing working.

I have not reached the 5000 limit and do have a valid access code.

This is the link I used for the API https://api.ebay.com/sell/inventory/v1/inventory_item/

When I use the API Explorer (https://developer.ebay.com/DevZone/build-test/test-tool/default.aspx?index=0&api=inventory&call=inventory_item-sku__PUT&variation=json&env=production) I get the same error but it says Can not instantiate value of type:

{
  "errors": [
    {
      "errorId": 2004,
      "domain": "ACCESS",
      "category": "REQUEST",
      "message": "Invalid request",
      "longMessage": "The request has errors. For help, see the documentation for this API.",
      "parameters": [
        {
          "name": "reason",
          "value": "Can not instantiate value of type [simple type, class com.ebay.raptor.slrinvapi.app.entities.InventoryItem] from JSON String; no single-String constructor/factory method"
        }
      ]
    }
  ]
}

This is the code but without the client id and client secret:

import requests
import json
import base64

client_id = '#################################'
client_secret = '#################################'
redirect_uri = 'https://amazon.adamkhattab.co.uk/callback.php'

auth_url = 'https://auth.ebay.com/oauth2/authorize'
token_url = 'https://api.ebay.com/identity/v1/oauth2/token'
api_url = 'https://api.ebay.com/sell/inventory/v1/inventory_item'

def get_access_token(client_id, client_secret, redirect_uri):
    auth_code = input('Please enter the authorization code: ')
    headers = {
        'Content-Type': 'application/x-www-form-urlencoded',
        'Authorization': f'Basic {base64.b64encode(f"{client_id}:{client_secret}".encode()).decode()}'
    }
    data = {
        'grant_type': 'authorization_code',
        'code': auth_code,
        'redirect_uri': redirect_uri
    }
    response = requests.post(token_url, headers=headers, data=data)
    access_token = json.loads(response.text)['access_token']
    return access_token

def list_item(access_token):
    headers = {
        'Authorization': f'Bearer {access_token}',
        'Content-Type': 'application/json',
        'Accept': 'application/json'
    }

    data = {
        "title": "Bluetooth Speaker",
        "condition": "NEW",
        "description": "This is a very good speaker and sounds amazing",
        "imageUrls": [
            "https://amazon.adamkhattab.co.uk/photo.jpg"
        ],
        "price": {
            "value": "20.00",
            "currency": "GBP"
        },
        "quantity": 1
    }

    response = requests.post(api_url, headers=headers, data=json.dumps(data))
    print(response.text)

auth_url += f'?client_id={client_id}&redirect_uri={redirect_uri}&response_type=code&scope=https://api.ebay.com/oauth/api_scope/sell.inventory'

print(f'Please visit the following URL and authorize the application:n{auth_url}')
access_token = get_access_token(client_id, client_secret, redirect_uri)
list_item(access_token)