This is how you get access to your test account’s page:

1. Go to developer.paypal.com
2. Go to Applications
3. Click on Sandbox accounts
4. Choose Log In with PayPal (use your regular account – not the Sandbox one)
5. (Optional) Import your old accounts from your former Sandbox account after the redirect to the accounts page
6. Click on the account you want to log in to
7. Choose “Sandbox site”
8. Log in to that site using your test account