Missing class need advice

I am currently a 2nd year at the architecture school. I'm supposed to be taking a History of architecture introductory course. The course is currently full and I'm pretty sure the Add/drop period has passed. However Ive been emailing advisors and nothings been working. I need this course as a prerequisite for two other courses, and I need to do these courses on time as at the end of third year there's a review that results in whether or not you progress to the fourth year. I was wondering if anyone has any advice. Im currently talking to another classmate going through this aswell.