Mypack sometimes seems to indicate there are seats available, but won't let you register. The interface of Mypack can be misleading, which is usually the problem.
Let's take an example. The following indicates there are 7 seats available in course csc576:
This should properly be interpreted as meaning "the total available seats across all cross-listed versions of this section is 7".
If the link "001-LEC(10808)" is clicked, the next screen tells the story:
From this, it may be seen that the CSC version of this cross-listed course has seats available, but the ECE version does not. A CSC student would be allowed to register in CSC576-001, but an ECE student would not be allowed to register in ECE576-001, even though the first screen showed seats available. You sometimes have to click the link for more detailed information to understand the reason you are not allowed to register for a course.
It is unfortunately true that courses do fill up. We attempt to predict demand and provide sufficient capacity, but are not always successful. We also monitor enrollments after registration is open, and where possible will add capacity to meet demand. Room capacity is a limiting factor, particularly for courses taught in an Engineering Online studio classroom. We will not expand course capacity beyond the limits of the room size.
Your options are
The Computer Science Department welcomes interest by non-majors in its courses, but gives priority for enrollment to Computer Science majors. The way this is managed is that only Computer Science and Computer Networking majors can enroll themselves directly in Computer Science graduate courses (using Mypack). Non-majors who wish to enroll must wait until one week before the start of the semester. At that time, they should email their request, along with their student ID number and proof that they meet the course prerequisites (e.g., transcripts), to the Computer Science Graduate Office (firstname.lastname@example.org). If there are open seats, they will be enrolled. A staff member will mail back the results.
The only exception to the above is that by special arrangement, Computer Engineering PhD students are allowed to register without being required to wait. Again, they should email their request, after registration has opened, to the Graduate Office staff.