Access Denied to ATLAS

I was completing a training on ATLAS when something strange occurred. I just finished one of the quizzes and clicked "Next" to continue with the training. The window went blank with a loading symbol that lasted for quite a while. I tried refreshing the window, to no avail. Then, I tried opening ATLAS in a new window. This time, after signing in, I received this error message: "Access denied. Your account does not have permission to access ATLAS application." What should I do?