You are only guaranteed a place in a compulsory course if you registered for it during the official registration period.
If you didn't register for courses in semester 1 (Bachelor's) or semester 1 period 1 (Master's) 2021-2022, then you can register during the late course registration that runs from 31 August 8 A.M. - 10 September 13 P.M..
Course registration is subject to availability. There is always a spot in mandatory courses of the curriculum, sometimes via a waiting list.