Registered for over 19 credits?
If you are registered for more than 19 credits and have not received advisor approval, it is especially urgent that you contact your advisor to discuss (a) getting their permission to drop a class using the online drop process or (b) getting their support and petitioning for after-the-deadline approval for over 19 credits. If you remain in over 19 credits without approval, the registrar will automatically drop you from your most recently-added course(s). Haven't met with your advisor for schedule approval?
As a reminder, all students were supposed to meet with their advisor sometime during the first two weeks of classes to get the advisor's sign-off on your final schedule. If you haven't yet done that, it's not too late, but you should contact your advisor for a meeting ASAP.