Quick tip: use a course-friendly browser like Google Chrome or a non-company linked computer.
This is likely due to either your browser or cache.
Sometimes working through a "virtual office" on your company's computer will block video playback for security reasons; however if you go into "incognito" mode it should correct the issue.
If this persists, please attempt using a course-friendly browser such as Google Chrome OR working on a non-company linked computer. The next step would be to clear your cache, by going to settings of your browser and removing its logged cache backup.