When you embed videos from websites, such as YouTube and Vimeo, in Storyline 2 courses, you may find the fullscreen button for these videos is either missing or doesn't work in your published output.
For security reasons, many web browsers are now restricting fullscreen mode for embedded iframe content.
We provided a programmatic solution for this issue in Update 10 for Storyline 2. Install the latest version of Storyline 2 to take advantage of the new features and fixes, then republish your course.
Note: Some LMSs, such as SCORM Cloud, don't allow website videos to toggle into fullscreen mode.