I’m running an iMac OS 10.13.6 (Retina 4K, 21.5-inch, Late 2015) with a 3.1 GHz Intel Core i5 processor. I have been using the Client BOINCmanager now for ten years or more. Suddenly when I went to upgrade to BOINC 7.12.0 (64-bit Intel) I get this message:

“The application “BOINC Installer.app” can’t be opened”.

I have tried everything I can think of. No go! Anyone else have this problem? I can't even go back to an older version.

If not tried yet, try downloading the installer again.

https://boinc.berkeley.edu/download_all.php has all the installers, also the ones from before.

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Been there, done that. Even down loaded an older version and got same message! I’ve tried 32 and 64 bit! No go! Same Message. Even checked to see if my Stuffit Expander was the latest.

Having searched for it, it would seem that the error message that you receive is about BOINC not being from the Mac App Store which is resulting from a setting on your Mac. The default is what it is set at now: OS X will not allow you to install applications that came from anywhere but the Mac App Store. You can update that setting by opening System Preference and selecting "Security & Privacy", then check what's set at "Allow apps downloaded from", set it to Anywhere.

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When Sierra 10.12.0 came out apple took away the “Allow apps download from: anywhere”. There is a procedure that I went through, using the “Counsel.app” of getting it back and setting it on “from anywhere”. Still no go! Ripping what little hair I’ve got out! Have you heard of this problem?

Found this on a Mac forum:

It looks like executing the application is a fail. I think that you just need to chmod it to make it executable.

STEPS:

1. Open a terminal

2. Here are the commands:
cd
cd Applications
cd APPLICATION_NAME.app (where APPLICATION_NAME is your app)
cd Contents/MacOS

First Option (if you know which is the executable): chmod +x FILENAME (where FILENAME is the name of the executable)
Second Option (if you don't know which is the executable): chmod +x *

If it tells you operation not permitted, then add sudo in front of chmod

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And make sure you followed the right procedure, see for instance this Youtube video on how to manually get "from anywhere" back.