I can see the download here, but I can’t watch the video
Are you able to view other mp4 files? If not, you may need a plugin for your quicktime program. You may be missing the codec that plays MP4 videos (that’s the format of the downloads).
To bypass the Quicktime troubleshooting, VLC is a free player to add to your Mac. It will play pretty much anything and is very popular.
Here’s how to check the Quicktime codec:
Download and test the file sample_mpeg4.mp4 here and you’ll know if this is a quicktime issue.
Here’s the paid Quicktime add-on page.
Here’s a free download from the quicktime forum that may work for you.