I’ve been dealing with this problem for over a month now. I can no longer edit courses, add lessons, or modify lessons. I’m forced to uninstall the plugin. They can’t seem to find a real solution. I’ve also updated the plugin to version 3.1.0, but nothing has changed (in addition to following their advice).
Adding a lesson: https://prnt.sc/o7E0QMEHUe9Z
Editing a lesson: https://prnt.sc/PCMMJVryOlNT