openings / seats

1a. You didn’t enroll in this course because there were no openings.
1b. You didn’t enroll in this course because there were no seats.
2a. There is a lack of university openings for students currently.
2b. There is a lack of university seats for students currently.
Please correct and comment.
Thanks.

1a. You didn’t enroll in this course as there were no places.
1b. You didn’t enroll in this course because there were no seats.
2a. Currently there is a lack of university places for students.
2b. Currently there is a lack of university seats for students.

Note the spelling:
enrol - BrE
enroll - AmE