When trying to install software from App Store on OS X 10.11, I get the error message "The product distribution file could not be verified. It may be damaged or was not signed." I have tested several different pieces of software, and get the same issue on all of them.
I have found a few suggested solutions, however they are from 2011, and refers to the /var/folders, which El Capitan does not have (I can't remember when it disappeared, but I think it was some time ago).
In the system logs, I see the following each time I get the error:
09/10/15 19:28:04,476 storedownloadd: *** Assertion failure in -[CheckPreflightOperation verifyDistributionAtURL:allowsDevSign:allowsUnsigned:osVersionToBeInstalled:error:distributionController:], /Library/Caches/com.apple.xbs/Sources/Commerce/Commerce-453/CommerceKit/CheckPreflightOperation.m:291
When I browse to /Library/Caches, I do not see com.apple.xbs.
As my first attempt to resolve this issue, I renamed /Caches to /Caches_old (paranoid, I guess, but the practice has stood me in good stead previously, so I think it's not the worst idea in the world), then closed and reopened App Store, and retried the installation.
I was now prompted to re-enter my iCloud password. I did so, and was presented with a new error message: “%Program% failed to download. Use the Purchased page to try again. In the Purchased page, the program had a line next to it, saying “An error has occurred”.
Once more consulting Console, I get this:
09/10/15 20:22:16,130 sandboxd: () storeaccountd(314) deny mach-lookup com.apple.backupd.sandbox.xpc 09/10/15 20:22:17,347 storedownloadd: SSDownloadAsset caching-server-locator-timeout 10
I tried renaming the old Caches-folder to Caches - no go.
I tried renaming the Caches-folder to Caches_Old, and then creating a new Caches-folder - no go.
I rebooted the computer - no go
I renamed the new Caches-folder to Caches_older, then renamed the Caches_old-folder to Caches, and rebooted - no go
Update: I have also tried renaming the Caches-folder, and then rebooting. A new Caches folder is then generated, but the problem remains the same.
Update 2: I have tried starting the Mac in safe mode and trying it there. The error still persists, but now I get a new error:
12/10/15 21:12:20,744 sandboxd: () ReceiptInstaller(500) deny mach-lookup com.apple.DiskArbitration.diskarbitrationd 12/10/15 21:12:24,747 storedownloadd: AssetDownloadOperation no modified URL for http://osxapps.itunes.apple.com/apple-assets-us-std-000001/Purple/99/60/6a/mzm.zqwtwhxj.pkg