

When I extract on a Windows-PC and compress again the same file on the WIndows-PC, the resulting zip can be read normally by the Mac. It's just the format QNAP produces, which Apple doesn't like. I made several tests and found that the file is really downloaded correctly by both OS. You cannot extract the zip on an Apple-Computer. But when you download from a Mac, it won't work. This is useful for sending files online or to store files you no longer need. The problem is: This zip-file is perfectly readable and extractable from a Windows-PC. You can also decompress any ZIP file by simply double-clicking it. If the file is from a trusted site, double-click it to decompress. The downloaded file may be a compressed archive or disk image that contains the file you want. If your Mac is running an earlier version of the macOS software: On your Mac, open the App Store and click the Updates tab. If there is an update, click the Update button. Delete it, then try downloading it again. If your Mac is running macOS Mojave or later: Click the Apple menu and go to System Preferences and Software Update. If you do, the file may have been corrupted during the download. zip files earlier before formatting the phone, once I formatted the phone I am unable to open. Make sure you have the app needed to open the file. In this case, QNAP automatically zips the selected files and you download just the (one) zip-file. I am not sure, if this is the new updateI was able to open. Problem description: When using the integrated "Web File Manager" provided by QNAPs software, there is also the possibility to select multiple files and download them at once with a single mouseclick.

it describes exactly the problem I have with the most actual software of QNAP (3.7.3). I found this (rather old) thread by searching the forums.
