getting service unavailable and internal server error and JSONDecodeError at /pay/ while integrating phonepe in my django project

Question

this is my code please check it once I am getting error at pay function of this code and at this line responseData = response.json()

def calculate_sha256_string(input_string):
    # Create a new SHA-256 hash object
    sha256 = SHA256.new()
    # Update hash with the encoded string
    sha256.update(input_string.encode('utf-8'))
    # Return the hexadecimal representation of the hash
    return sha256.hexdigest()

def base64_encode(input_dict):
    # Convert the dictionary to a JSON string
    json_data = jsons.dumps(input_dict)
    # Encode the JSON string to bytes
    data_bytes = json_data.encode('utf-8')
    # Perform Base64 encoding and return the result as a string
    return base64.b64encode(data_bytes).decode('utf-8')

def pay(request):
    MAINPAYLOAD = {
        "merchantId": "PGTESTPAYUAT",
        "merchantTransactionId": shortuuid.uuid(),
        "merchantUserId": "MUID123",
        "amount": 10000,
        "redirectUrl": "http://127.0.0.1:8000/return-to-me",
        "redirectMode": "POST",
        "callbackUrl": "http://127.0.0.1:8000/return-to-me",
        "mobileNumber": "9999999999",
        "paymentInstrument": {
            "type": "PAY_PAGE"
        }
    }
    # SETTING
    INDEX = "1"
    ENDPOINT = "/pg/v1/pay"
    SALTKEY = "099eb0cd-02cf-4e2a-8aca-3e6c6aff0399"
    base64String = base64_encode(MAINPAYLOAD)
    mainString = base64String + ENDPOINT + SALTKEY
    sha256Val = calculate_sha256_string(mainString)
    checkSum = sha256Val + '###' + INDEX
    print("Checksum:", checkSum)
    # Payload Send
    headers = {
        'accept': 'application/json',
        'Content-Type': 'application/json',
        'X-VERIFY': checkSum
    }
    payload = {
        'request': base64String
    }
    print("Sending request to PhonePe API:")
    print("URL:", 'https://api-preprod.phonepe.com/apis/pg-sandbox/pg/v1/pay')
    print("Headers:", headers)
    print("Payload:", payload)
    response = requests.post('https://api-preprod.phonepe.com/apis/pg-sandbox/pg/v1/pay', headers=headers, json=payload)
    print("Raw Response Content:")
    print(response.text)
    responseData = response.json() #getting error here
    print("Response from PhonePe API:")
    print(responseData)

    # Print the raw response content

    redirect_url = responseData['data']['instrumentResponse']['redirectInfo']['url']
    print("Redirect URL:", redirect_url)

    return redirect(redirect_url)

def payment_return(request):

    INDEX = "1"
    SALTKEY = "099eb0cd-02cf-4e2a-8aca-3e6c6aff0399"
    form_data = request.form
    form_data_dict = dict(form_data)
    # respond_json_data = jsonify(form_data_dict)
    # 1.In the live please match the amount you get byamount you send also so that hacker can't pass static value.
    # 2.Don't take Marchent ID directly validate it with yoir Marchent ID
    if request.form.get('transactionId'):
        request_url = 'https://api-preprod.phonepe.com/apis/pg-sandbox/pg/v1/status/PGTESTPAYUAT/' + request.form.get('transactionId')
        sha256_Pay_load_String = '/pg/v1/status/PGTESTPAYUAT/' + request.form.get('transactionId') + SALTKEY
        sha256_val = calculate_sha256_string(sha256_Pay_load_String)
        checksum = sha256_val + '###' + INDEX
        # Payload Send
        headers = {
            'Content-Type': 'application/json',
            'X-VERIFY': checksum,
            'X-MERCHANT-ID': request.form.get('transactionId'),
            'accept': 'application/json',
        }
        response = requests.get(request_url, headers=headers)
        #print(response.text);
    return render('main/try.html', page_respond_data=form_data_dict, page_respond_data_varify=response.text)

this is my code

i tried everything i just want to it to open the payment screen in front of me i dont know if the error is from my side or from phonepe side it is showing the error is in this line responseData = response.json()