Thank you, that satisfies my curiosity. I don't blame you for moving on to a new version, which I'll upgrade to when I move up to El Cap.

I figured it had something to do with a change in the Mac OS. One of the things that I find crazy about "OS X" (again, neither here nor there.. just whining)  :@   is that they have made a ton of major changes that should have warranted a new version the OS. For example, the move to Intel should have moved OS X up to OS XI (Eleven), and so on. You doing a re-write of Cookie's code warrants a version change (rather than an incremental version update to Cookie 4). When Apple issues an update of OS X, it's hard to tell if it's a just a few tweaks here and there, or they've thrown the baby out with the bathwater.

Anyway, thanks for responding, and thanks for putting up with my off-topic whining about Apple. 

Could you explain why Cookie 5 is only compatible with OS X 10.11 (El Capitan) and above?  I recently bought a new MacBook, which came loaded with 10.10.x Yosemite. Only a few months later, I'm already running into software (on the App Store and elsewhere) that is not backward compatible to even one OS earlier.

I'm a little frustrated at how often Apple deprecates or abandons OS X features and other things like peripheral interfaces, etc. What is it about El Capitan that prevents Cookie 5 from being backward compatible with Yosemite? Put another way, why can't Cookie 5 run on Yosemite?

Obviously, I'm assuming that Apple is the reason, but if there's some other reason for limiting Cookie 5 to El Capitan, I'm curious to know why that is as well. I was unable to glean a connection from comparing the lists of new features of both El Capitan and Cookie 5.

(Note: Neither here nor there, but I would upgrade to El Capitan if there weren't currently 605 one-star reviews compared to only 480 five-star reviews. That alone is enough of a reason to hold off on upgrading for now).

Thank you very much, Russell, the delete and re-install method worked for Cookie, and one other app that (after I posted) did the same thing.

A more recent article on iMore explains what happened and includes an update:

Here's What's Happening

Within about 6 hours, Cookie stopped working on both my MacPro and my MacBook Air. This is the pop-up message I received both times:

'Cookie.app' is damaged and can't be opened. Delete 'Cookie.app' and download it again from the App Store.

These two computers are not networked with each other (no sharing, separate externals) but share the same router/internet connection. I only use the MBA about twice a month.

What could cause an app to get nuked on two different computers at essentially the same time?

From MacBook Air Console log:

11/12/15 3:02:23 PM com.apple.launchd.peruser.501[119]  ([0x0-0x18018].com.sweetpproductions.Cookie [169]) Exited with exit code 173

From Mac Pro Console log:

11/13/15 9:10:00 AM	com.apple.launchd.peruser.502[298]	([0x0-0x24024].com.sweetpproductions.Cookie[391]) Exited with exit code: 173


Mac OS X 10.6.8
Cookie 4.3.3```

Note: The versions I'm running should have nothing to do with a simultaneous app failure on two separate machines, unless there was a security hole that was closed by later versions. If this was the result of an attack, I'm interested in finding out what I should look for, or whether anyone has an idea of what else could possibly cause this. I've run virus and malware utilities, repaired permissions and deleted App-related p-lists. 

I cannot (for my own reasons) update the OS, but can update Cookie. However, updating is not a recommendation I'm looking for. I will update. I'm looking for possible reasons why, because this is a very odd thing that has never happened to me before. Any ideas?