I finally figured out what U of T means by an "activity code". Turns out
it's just the course code. I was thrown off because York had course codes,
and then another code that you had to type in to register. So I thought the
"activity code" was something different (because if they meant course code
they'd just say course code, no?) and was going through all my U of T
propaganda to find activity codes until the correct answer occurred to me in
the shower this morning.

So then, correct code in hand, I go to register. It won't let me. I look
to see if the course is full. It says the course doesn't exist. I look to
see if the course has been cancelled. It hasn't been. Turns out that at U
of T you aren't allowed to register for anything at all between August 16
and 23. Who ever heard of a random week of non-registration in the middle
of August? It's bad enough that ROSI closes down overnight, but to not
accept registrations just for the sake of it, and make it so students can't
even see if there's room left in a class?

I'm so glad that this course does not matter in the grand scheme of things,
or I would be seriously stressed!