With Dropbox you have the option to download single files or all files as a zip archive (Download as .zip) when someone shares files.
Problem is that Opus wont extract the downloaded zip archive. "An error occured reading archive: the archive appears to be invalid or damaged" The archive isnt damaged as other ZIP managers extract it just fine. This happens every time when another Dropbox user shares a download link and I use the particular download option. Only thing i can find is that the extracted zip archive (extracted through 7-zip) contains an empty directory named as the zip file itself.
When i select a directory on my own Dropbox webpage and right click it, the zip archive downloads and extracts fine.
Now i cannot share the particular link because of confidential files, but maybe someone can test this.
Dropbox has been creating invalid archives for years. If it's the same problem as before, they put all the files below a top-level folder with a null (zero length) name, which is completely illegal and illogical.
Opus rejects such archives in case they are security exploits (since there have been exploits in the past using invalid file/folder names in archives).
The problem should be reported to Dropbox so that they might fix it.
We'll look at making this work in the next update, as I agree it's unlikely Dropbox would do anything about this.
Interestingly, it only seems to happen if the zip file is created via a shared link. If you go to your own Dropbox page and download a zip file that way, it works fine in Opus. So they are obviously using different code in the two cases.