The client interface has infoboxes which ask/suggest that the user take an action. Sometimes, these are mandatory in order to proceed, like this one:

"A link was sent to the email address you provided. Please click the link in the email to verify your email address before proceeding to make payment."

There are a few ways that the UI's design could make it more obvious that an action is mandatory, to prevent confusion where the user clicks a button ("Continue" in this case) and nothing happens:

• These could be modal, rendering front and center while the rest of the page's content dims out.
• These should not be dismissable with the "X" in the upper right.
• An additional error message, animation, or conspicuous (e.g. bold / red) text could highlight the problem when "Continue" is clicked without the action having been satisfied.