Error accessing the binary

For reasons known only to macOS developers at Apple, sometimes the app is kept in quarantine after being downloaded using Safari.

This sometimes results in an error accessing p7zip or any of the other Keka bundled binaries:

Removing the quarantine flag

You'll need to manually remove the quarantine flag, as follows:

1. Quit Keka
2. Open the Terminal.app, found in the Applications/Utilities folder
3. Execute the following command: xattr -d -r com.apple.quarantine /Applications/Keka.app
4. Quit the Terminal.app
5. Open Keka