OAU-213 TokenInvalid, while calling refresh token

We are using the OAuth Authorization Code flow, although while calling the refresh token, even when the refresh token is valid.

The access token is valid and works with other APIs when it is valid, although when we call API for a refresh token, it is giving us an invalid token.

I checked the forum for the solutions, although neither the token seems to be corrupted, nor the password has changed. Can you please assist us with the same?

I am attaching the code for the same below:

Authorization Code to get access token:

self.url = f"{self.API_Server_URL}/restapi/oauth/tok
clientId_clientSecret =f"{self.rc_clientId}:{self.rc_clientSecret}"
clientId_clientSecret_bytes = clientId_clientSecret.encode("ascii")
base64_bytes = base64.b64encode(clientId_clientSecret_bytes)
base64_clientId_clientSecret = base64_bytes.decode("ascii")

            headers = {
                "Authorization": f"Basic {base64_clientId_clientSecret}"
            }

            params = {
                "grant_type": "authorization_code",
                "code": code,
                "redirect_uri": self.redirect_uri + "/ringcentral/auth",
                "client_id": self.rc_clientId,
                "client_secret": self.rc_clientSecret,
                "refresh_token_ttl":604800
            }

            responseData = requests.post(self.url, headers=headers, data=params)

Code used for getting refresh token:

clientId_clientSecret = f"{rc_clientId}:{rc_clientSecret}"
 clientId_clientSecret_bytes = clientId_clientSecret.encode("ascii")
            base64_bytes = base64.b64encode(clientId_clientSecret_bytes)
            base64_clientId_clientSecret = base64_bytes.decode("ascii")
            brand_type = obj.get('brand_type')
            
            url = f"{API_Server_URL}/restapi/oauth/token"

            if brand_type:
                url = url.replace(".com", ".biz")

            headers = {
                "Content-Type": "application/x-www-form-urlencoded",
                "Accept": "application/json",
                "Authorization": f"Basic {base64_clientId_clientSecret}"
            }
            params = {
                "refresh_token": obj.get("refresh_token"),
                "grant_type": "refresh_token",
                "endpoint_id": obj.get("endpoint_id")
            }

            responseData = requests.post(url, headers=headers, data=params)