bensly I remember you told having done Rollover yet, right?
You cannot create users in Moodle from previous school years unfortunately.
Your best option is to rollback to a database before Rollover, or start over again I am afraid.
It is clearly mentioned in the README:
Note: it is not possible to create a User or a Course, or enroll a Student in Moodle from previous school years (after Rollover).
I'll add a link to the Database Backup program on the Rollover screen and help to invite users to perform a backup before performing Rollover.