How do I open pw protected zip file?

AFAIK, the only Mac tool that *claims* to be able to open 7Z files is SmartZipper: Smart Zipper - Compress, decompress Zip, 7Z, Rar files on the Mac App Store

I've never used it myself, so check with the developer if it indeed does what you want.

I just created a 7-zip archive here with an older tool, added password, and wrote out the 7z file to my Desktop. I right-clicked on this file, chose Open with, and using TheUnarchiver, was able to supply the password and extract the content correctly. On OS X El Capitan 10.11.6.

Although I have Windows 10 running here in a VM, I do not have any 7-zip tool on it to further test platform issues.

The error message implies it is using a (presumed) newer variant of .7z than the Mac tools you have tried support. I encountered a similar issue with a .rar file recently which was in the new version 5 RAR format.

Whilst there are at least two tools that I know now support v5 of RAR on a Mac I do not what format/version your file is in and whether any Mac tools support it. You can see information about the .7z format here http://www.7-zip.org/7z.html

The same website lists various .7z tools that either they provide or recommend. The only Mac tool listed for .7z files is Keka which is what I have myself used in the past. The current version of Keka is 1.0.9 but there is a Keka 1.1.0beta which you could also try. See http://www.kekaosx.com/en/

Most compression tools and formats actually have multiple different compression schemes they can use although most of the time these choices are hidden and unnecessary. Zip has multiple variants, RAR has and so does .7z, if you look at the first webpage I linked to i.e. the .7z website you can see it lists at least seven different versions it can do. When you created a new test file and then successfully opened it you will have created it using a variant your tool understood, the problem here seems to be it has been created with a more esoteric or newer variant than the Mac tools you have tried understand.

If the latest or beta Keka cannot open it then you may need to try using a PC or Windows in a virtual machine, or ask the sender of the file to redo it in a different format.

FWIW, I just created a few .7z files using 7-Zip on Windows 7 using AES256bit compression. The Unarchiver had no trouble decrypting and opening the files.

Anything "unusual" about the password you are using such as special characters?

One of the formats for .7z seems to be for .exe files which of course are for Windows only. Perhaps Mac .7z tools omit this option because .exe files are irrelevant to Mac.

Sounds like either you will have to use Windows or get them to redo it as I suggested.

Your mentioning using 7zip under Windows has probably confused a few of us in to thinking this was to do with a .7z file.

The .zip format is actually 'owned' by a company called WinZip. They have their own product they sell and also sell a Mac version. See http://www.winzip.com/mac/en/

As mentioned .zip also has multiple varieties. You could try the trial Mac product from the above.

.zip and .7z are really two totally different formats.

A common mistake by Windows users is putting the wrong file extension on files. If they used 7zip to create a ZIP file but used the .7z file extension this would confuse other more law abiding tools and equally possible would be the reverse of them having used 7zip to create a .7z file but using the .zip file extension.

You could as a last resort therefore try on the Mac altering the file extension from .zip to .7z and then re-trying Keko.

However I believe you said you had managed to process this file on a Windows PC so this would be more helpful next time around.

(Mac users do not get off scottfree, they sometimes have the distressing habit of not putting a file extension on files at all.)

The Unarchiver, also in the Mac App Store indicates that it unzips 7-zip files.

Yes, it's the algorithm. Another one you can try: http://www.kekaosx.com/en/