Thanks for the link Mark!
If I recall correct that user submitted a ticket and we were able to get his issues resolved. We originally thought it was on the browser end via a thread similar to this:
https://kb.mozillazine.org/Source_file_could_not_be_read
But we discovered that their host was blocking part of the download due to a download cap the host had imposed on the server end. Something we really can’t solve in the plugin. That post was pretty old so it may have been someone else.
I do recall having helped others work with there hosts to solve the issue. Also if the server is preventing the download button from working, you can always get the installer and archive file from the wp-snapshots directory via FTP.
There are some other users I have helped as well were we had to adjust Apache to support the correct mime type (but I’m not 100% sure if that is the case for this issue). Some server configurations are very difficult to detect. This is why is some cases we have to get the host involved. We have tried to make the plugin simple, but there are allot of complexities to making it work on all the different server configurations.
Anyways sorry you had a bad experience, the plugin is by no means perfect but is getting better over time!
Cheers~