Nulumia
Customer
This is based on two local installations, including a fresh install on new XF instance.
When choosing Add Download -> Attachment based -> Attach multiple zip files for a version, none of the download buttons work on the "Choose version.." page:

When I click Download for any file, it slightly tweaks the URL bar and appears to load something for a moment, then does nothing. However downloading the single file under "Full file package" in the example above does work. So it appears to fail only on multi-attachment versions.
When choosing Add Download -> Attachment based -> Attach multiple zip files for a version, none of the download buttons work on the "Choose version.." page:

When I click Download for any file, it slightly tweaks the URL bar and appears to load something for a moment, then does nothing. However downloading the single file under "Full file package" in the example above does work. So it appears to fail only on multi-attachment versions.