Why?

As indicated in the image you've linked, the files are unable to be downloaded. The reason for this is listed:

Unable to download file. This could be due to a proxy or network issue or the hosting server not permitting downloads from your location.

I run into this issue occasionally when attempting to download from my corporate network. The answer for me, is to use a different location to download.

How and where are you downloading? IE, what type of network, and what country?