ZohoOAuthException Caused by:'Exception while fetching access token from refresh token

ZohoOAuthException Caused by:'Exception while fetching access token from refresh token

Hi !

We are implementing ZohoCRM into our Laravel (5.7) application 
We are using ZohoCRM sdk and we are using database for persistence but when we use Sdk for more then 5 times it gave us error (which i included as screen shot)

Because of lack of PHP SDK support and difficult to find any solution , there are no way or solution that can help us

Below is the snippet's which we are using in order to make this issue fixed
  1.         ZCRMRestClient::initialize();
        $oAuthClient = ZohoOAuth::getClientInstance();
        $grantToken = "1000.0613b6872e6d8bafb948141f9350fd2c.455fd34a33205a69b37a950400ed6789"; 
            $oAuthTokens = $oAuthClient->generateAccessToken($grantToken)