Why crypto.com exchange marking this as a bad websocket request

Question

I am trying to use https://exchange-docs.crypto.com/spot/index.html#public-auth but when trying to authenticate myself, I am getting a "Bad Request" as a response with 10004 code. From the API docs, the code represents missing parameters.

I checked their sample request provided in document and I am sending all required parameters. I am trying to find out what is causing this so please any help will be appreciated.

request: '{"id": 1, "method": "public/auth", "api_key": “<actual key>”, "nonce": 1646344180357, "sig": “<computed signature>”}’

response: {"id":-1,"code":10004,"method":"unknown","message":"bad request: {"id": 1, "method": "public/auth", "api_key": “<key>“, "nonce": 1646344180357, "sig": “<sig>“}”}

Code:

class CryptoAPIClient:
    __id = 0

    def __init__(self):
        try:
            self.ws = websocket.WebSocketApp(MARKETBASEURL,
                                             on_open=self.onOpen, on_close=self.onClose, on_message=self.onMsg)
            self.ws.run_forever()
        except BaseException as e:
            print(e)

    #when wesocket connection opens, send request with authentication info
    def onOpen(self, ws):
        auth_req = {
            "id": self.getNewId(),
            "method": "public/auth",
            "api_key": APIKEY,
            "nonce" : self.getNonce(),
        }
        payload_str = auth_req['method'] + str(auth_req['id']) + auth_req['api_key'] + "" + str(auth_req['nonce'])

        auth_req['sig'] = self.__makeSig(payload_str)
        #also tried adding endpoint to url by ws.url += /public/auth
        ws.send(json.dumps(auth_req))
        #sleep for 1 second as per crypto.com recommendation
        time.sleep(1)
        print("Opened a webscoket connection")

    #when connection is closed
    #NOTE: for some reason this is not getting called!!
    def onClose(self, ws):
        print("Closed connection")

    #when message is received
    def onMsg(self, ws, msg):
        print("message received: " , msg)

    #id for new websocket request
    def getNewId(self):
        if self.__id <= 1000:
            return self.__id + 1
        else:
            return 1

    #get nonce
    def getNonce(self):
        return int(time.time() * 1000)

    #create a signature for the request
    def __makeSig(self, payload_str):
        return hmac.new(
            bytes(str(SECRETKEY), 'utf-8'),
            msg=bytes(payload_str, 'utf-8'),
            digestmod=hashlib.sha256
        ).hexdigest()

Thank you very much!