Thanks for letting us know, I thought we had addressed these errors, but alas, clearly not.
While we are looking at getting this working, one of the work-arounds that often works is to log out and view the videos anonymously or in incognito mode. The site will pop up a window asking you to log in, but you can close that and still watch the videos. Right now at least, the issue seems to be related to being logged in and new lessons.
Thanks