This thread is in English, please continue in that language for the benefit of all reading.
I have just tested this plugin with Masterstudy LMS, and it works fine.
Inserting a protected video into a lesson using Shortcode:
Ensure to paste the Shortcode in the “Text” tab, not “Visual”. Then, back on “Visual” it should look like:
Viewing a protected video in a lesson:
This is the Masterstudy LMS default course that I imported.
Can you confirm you are running latest plugin version 1.8.1?
Please check “The display of the player is broken/it doesn’t work” question in the FAQ. Most likely another plugin is causing this issue.