For help with the student center, you can always call 800.576.GMAT or email
studentservices@manhattangmat.comIf you are having technical problems, you can also send an email to
helpdesk@manhattangmat.comAre you referring to the Challenge Problems? Anything you've purchased should appear in your student center. If you are referring to the Challenge Problems, there should be a link either on your student center home page or in the Homework & Practice section of your student center (on the right-hand side).