Can't watch and download video from iTunes I am experiencing a problem while trying to watch an iOS development course in iTunes on macOS. You can find the course here:

https://itunes.apple.com/ru/course/developing-ios-10-apps-with-swift/id1198467120?l=en

If I try to click the play button and watch videos 1 to 6, iTunes just does nothing. It seems to ignore my action. If I try to download the videos, it looks like they are downloading, but they turn out to have formatting problems. 

Here is a screenshot:

 

If I try to open this video I get this message:

The movie could not be opened.
An invalid public movie atom was found in the movie.


or this:

The movie could not be opened.
The file is not a movie file.


But interestingly, if I try watch online or download video from the 6th one to the last one they work properly. I can watch them as well as download them.

What is the issue here? What am I doing wrong?

If I skip something feel free to ask
I had this exact problem with the Stanford iOS 10 course on iTunes for Mac. I eventually gave up and downloaded the videos on iTunes for Windows.

However, I more recently fixed the problem by reinstalling macOS. You can do this by holding Command+R on startup, clicking on "Reinstall macOS" or "Reinstall OS X", and following the prompts.

Note that this will not destroy any of your files or programs. It simply reinstalls the system applications, but any settings, files, or applications that you have on your computer should not be changed.

(You may consider making a backup first.)