Since you are already registered for classes, you don't need to worry about taking the Math Assessment Test. Generally, the math test is available and requested for all incoming students, but, as you can see, it's not strictly required for placement.
The math test is used more as an auxiliary look at what you've retained from your prior math experience to help the Academic Adviser place you in the best class. If the best class is clear already from grades and test scores (SAT/ACT), then placement can be made without the Math Test score.