We have been able to replicate the issue on our end, our team is working on a resolution for this issue. For those experiencing the issue, please follow the steps suggested on this post for the Blizzard Application and for Diablo II, please refer to this thread.
Warcraft III and Starcraft I have transitioned over to the Blizzard Application. These classic application installations will install the Blizzard Application. Please follow the steps above.
If you have the application (or Diablo II) installed, this thread is not the appropriate thread. This thread is for failed downloads with the set up file in the browser. Please create your own thread or contact support.