Anyone encountered this before?
One user , El Capitan 10.11.5
Any Xojo app I send fails to open with a message saying This Application Cannot be Opened.
Its not the gatekeeper thing about code signing or downloaded from the internet.
Restarting the machine hasnt helped.
There is no such thing as Repair Permissions in disk utility any more.
Any clues?
Are you sure the user lets the download reach completion ?
Yup.
The apps were sent in a zip file.
An incomplete zip wouldnt even open, I believe
Can your user right-click the .zip and “open with → archive utility”?
i’ve seen users not being able to open an .app because they extracted the .zip containing the application with some other “extracting utility/app”.
Is he starting it from a Dropbox folder perhaps? Or moving things around using Dropbox?
I see it sometimes when an App is shared that way. Not always but every now and then. I think it has to do with Dropbox removing symbolic links and setting the flags incorrectly. (you can see it because the App size is much larger because the Framework is in there twice)
I like this idea.
I can see that a non-standard extractor could lose the exec permissions.
I’ll give that a try …
Is he running the right OS version?
Most recently I asked then to double click the application itself found by opening the packaged and drilling down into the contents.
THAT gives a message to say the app is damaged and cannot be opened, but tellingly it also says ‘created by Rar-7z Extractor on…’
So I am ‘happy’ that it is this unzipper that has failed to keep the exec permissions.
I have already told them to use Archive Utility, and clearly they havent.
But she’s not actually telling me anything, just sending screenshots of message that say ‘this isnt working’ in a varity of flavors.
Makes it a little hard to enagage… 
Looks like the argument against DMG just fell apart 
Ha ha… First time I’ve heard of such a tool, I wonder if it meddled with the OS and set it’s self as the default ZIP extractor. Or has incorrect UTIs forcing the system to believe that this is the default tool.
There’s zero reason why a unarchive utility on the Mac should use it’s own decompression for ZIP, the zip functions are built right into the OS.
Addendum:
Found it on the App Store, seems that it hasn’t been updated in 3 years and if it’s doing it’s own ZIP compression it’s not keeping up with the security standards.
https://itunes.apple.com/tw/app/rar-7z-extractor/id483293065?mt=12
It certainly helps to strengthen the argument for DMG, but this is the first time I’ve come across someone who’s using an antiquated custom ZIP decompression tool, which is where the problem lies.