If you select the 'Design Site' button and can't get into the Website Builder, it usually means a pop-up blocker is preventing you from accessing Website Builder.
Pop-up blockers can be hard to find and dis-able, so we've come up with an alternative solution.
Click on the 'Design Site' button three times in a row and it will bypass the popup blocker and take you to Website Builder in a web browser window.
Be aware, the browsers front/back arrow keys will not navigate as expected.
You can find more information at Pop-up Blockers.