Using python POST requests to buy a model

Hey, I’m looking for a fix on my script. Whenever I attempt to buy a model, it says
{"errors":[{"code":0,"message":"InternalServerError"}]}
Are there any fixes? I’ve tried everything

Here’s my current code:

import requests
import json

session = requests.Session()
session.cookies[".ROBLOSECURITY"] = "cookie"


def rbx_request(method, url, data, **kwargs):
    request = session.request(method, url, data, **kwargs)
    method = method.lower()
    if (method == "post") or (method == "put") or (method == "options") or (method == "patch") or (method == "delete"):
        if "X-CSRF-TOKEN" in request.headers:
            session.headers["X-CSRF-TOKEN"] = request.headers["X-CSRF-TOKEN"]
            if request.status_code == 403:  # Request failed, send it again
                request = session.request(method, url, data, **kwargs)
    return request

req = rbx_request("GET", "https://api.roblox.com/Marketplace/ProductInfo?assetId=903259919",data={})
y = json.loads(req.text)
url = f"https://economy.roblox.com/v1/purchases/products/{y['ProductId']}"
print(url)

req = rbx_request("OPTIONS",url,data={})
req = rbx_request("POST",url,data={"expectedCurrency":1,"expectedPrice":0,"expectedSellerId":y["Creator"]["Id"]})
print(req.text)