When trying to login with sandbox account in my simulator, nothing happens, it just become inactive for few seconds and then it become active again prompting that I can login, again and again.
Sandbox Account
In the sandbox, you can fetch in-app purchase information in the Simulator. However, you cannot purchase them.
To test purchasing in-app purchases in the sandbox, run your app on a device. For more information, see Testing In-App Purchases with sandbox.