Everything works fine in a development/localhost environment.

When deploying to heroku, using sandbox/test credentials on a new app, and creating a new payment I am getting 

```
A PayPal::SDK::Core::Exceptions::UnauthorizedAccess occurred in orders#create:

  Failed.  Response code = 401.  Response message = Unauthorized.

```

Again, everything thing works in a development environment

Should I permit any specific domains (like in Facebook integration)?