My AI chatbot script linked to GPT-2 API isnt working. Any help?

local HttpService = game:GetService("HttpService")
local API_KEY = "blanked out for privacy"
local API_URL = "https://api.openai.com/v1/engines/davinci/completions"

function generateText(prompt, length)
    local requestBody = HttpService:JSONEncode({
        prompt = prompt,
        length = length,
        temperature = 0.7,
    })

    local headers = {
        ["Content-Type"] = "application/json",
        ["Authorization"] = "Bearer " .. API_KEY,
    }

    local response = HttpService:PostAsync(API_URL, requestBody, headers)
    local responseData = HttpService:JSONDecode(response)

    return responseData.choices[1].text
end

local generatedText = generateText("Once upon a time,", 50)
print(generatedText)