A recent update of qSandbox that we've pushed a few days ago has introduced a cool glitch that prevented the auto login feature from working. So if you tried to log into your test sites from Dashboard > Admin that wouldn't work.
How to fix it?
a) Delete the test site and create a fresh one
b) Click on the Force plan reload button at the bottom on the Dashboard page.
It can take some time based on the number of tests sites you currently have.
Let us know if you're still running into any issues at http://qsandbox.com/app/contact.php