I don't have a solution, but I also ran into this same problem. And I was wondering if you were having this specifically same instance as me: In the launcher, there is a little cog at the top right that says " Modpack Options" and there you can go to your Modpack's Install Folder on your computer by selecting 'Open'.
Do you see your modpack's name in that folder (or more specifically, the name of your .zip file)? Mine is there for me and I see all of my original files. So the launcher did LITERALLY what the download link did and unzips it at the location. But, that doesn't properly disperse the mods to their locations.
If you are also having that problem, it doesn't seem like it's a download problem so much as it is the files are not going in the right place once downloaded.
