Hello, @soliman1
1)The “Not Found” error can be caused by permalinks. Please try to resave the permalinks in Settings -> Permalinks, and check again
2) You can try to use the Embed link from video-sharing websites such as YouTube or Vimeo.
For a sample, I’ll use the YouTube video. First, you need to click on the share button under the video – Screenshot, and use the Embed option – Screenshot.
Then select the URL as shown here Screenshot, the link must include the ‘embed’ word.
After this please edit your video lesson via frontend builder, click on Insert -> Media – Screenshot.
In General tab insert the link you just copied – Screenshot , then use the Embed tab and insert the whole embed code – Screenshot, Screenshot
The result – Screenshot
Also, you can have a look at our documentation about how to add the video lesson – https://docs.stylemixthemes.com/masterstudy-lms/lms-course-features/how-to-add-video-to-the-lesson.
In case of any difficulties with the MasterStudy LMS Pro plugin, you can easily submit a ticket on https://support.stylemixthemes.com/tickets/new and our support managers will be glad to help you.
Best regards