Let's check a couple of things: First, make sure the student is entering the exact code which is case-sensitive, but I'll bet you've already done that. Next, make sure the student is putting the code in the blue box and not the orange one; that's a common mistake (see screen shot). Finally, be sure the student hasn't placed a space anywhere because that will be seen as a character and cause a problem. What is the student's name so we can also check it on our end?