Classroom course with limited seats and different memberships

I want to implement the below scenario:
-Classroom course with a limit of 20 students in the class
-Students can either pay weekly or monthly for this course
-The important thing is that at any given time the students don’t pass 20 students.

I tried to implement this logic using LearnPress and Paid membership pro doing the following:
-Created the course in LeanrPress with limit of 20 students
-Created 2 membership levels for this course (weekly and monthly)

The issue is that for some reason when I buy any of the membership levels, the course student count doesn’t increment, so this leads to the possibility of buying more than 20 memberships.

Is there any other way (paid/free) achieving such logic ?