In the Sandbox mode you can use only the test buyer accounts. You are unable to sign in with a real buyer account.
In the Production mode you can use only the real buyer accounts. You are unable to sign in with a test buyer account.
In the Sandbox mode you can use only the test buyer accounts. You are unable to sign in with a real buyer account.
In the Production mode you can use only the real buyer accounts. You are unable to sign in with a test buyer account.