Facing error: Error Message: HTTP Status Code 400 Bad Request

I have created free trial account in ringCentral devolper beta and created sample app with Server/Web platform type and used your project to connect. Facing this exception:

```
Error Message: HTTP Status Code 400 Bad Request/n{
  "error" : "unauthorized_client",
  "error_description" : "Unauthorized for this grant type"
}
```

Please provide suggetion. Thanks in advance.
