I have installed moodle on an aws instance. I'm able to login and create users and courses as normal, but not able to add users to a course. 

The given api: /enrol/manual/ajax.php is returning 304, while when I tested on local instance it was giving 200 with modified count 1. 

The given url for enrolling users returns 304. 
https://moodle-dev.internal.quizizz.com/enrol/manual/ajax.php?mform_showmore_main=0&id=3&action=enrol&enrolid=4&sesskey=VXqWZZJikZ&_qf__enrol_manual_enrol_users_form=1&mform_showmore_id_main=0&userlist%5B%5D=4&roletoassign=5&startdate=4&duration=