Safari browser on iPad
To take Credentials tests on the Safari browser, make sure to unblock cookies from your browser prior to starting.
iOS 8 or later on iPad (see image above)
To set whether Safari blocks cookies in iOS 8 or later, go to iPad Settings, scroll down to find Safari, tap Safari.
Under the "Privacy & Security" section, tap Block Cookies and choose: Always Allow.
In iOS 7 or earlier, choose: Always
Alternatively, you may install the Chrome browser for iPad and use Chrome browser to take Credentials tests.
Safari browser on Mac
1) Click Safari in the upper left hand side of your screen. In the menu that appears, click Preferences.
2) In the window that appears, click the Privacy tab.
3) Next to Cookies and website data: select "Always allow"