This is the most frequently asked question for this app. Actually, in most cases, if a file is corrupted during the download process, it can not be unzipped by any application. The solution is to re-download the file and try to unzip it again. If this doesn't work, you can send the file to us to analyze the root cause.
In the Mac, due to permission issues, an application on the Mac App Store can not get the permission it needs to read files in the same folder automatically. The solution is to first add a permission or add all volume files into Oka Unarchiver. Then you can unzip it.