The product distribution file could not be verified

Several causes for this problem have been reported. Please take each of the following steps that you haven't already tried. Stop when it's resolved.

Step 1

If possible, test on another network, such as a public hotspot (if the computer is portable) or the hotspot created by a mobile device. A network gateway that blocks some traffic, most likely on a company or university network, could be causing the error.

Step 2

Back up all data.

From the menu bar, select

 ▹ System Preferences... ▹ Network

If the preference pane is locked, click the lock icon in the lower left corner and enter your password to unlock it. Then click the Advanced button and select the Proxies tab. If any proxy options are selected, make a note of them and then deselect them. You don’t need to change the bypass or FTP settings. Click OK and then Apply. Test. The result may be that you can't connect to any web server. Restore the previous settings if that happens.

Step 3

Rebuild the Spotlight index. If you try to search now from the magnifying-glass icon in the top right corner of the display, there will be an indication that indexing is in progress.

Step 4

Start up in safe mode and log in to the account with the problem.

Note: If FileVault is enabled in OS X 10.9 or earlier, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Ask for further instructions.

Safe mode is much slower to start and run than normal, with limited graphics performance, and some things won’t work at all, including sound output and Wi-Fi on certain models. The next normal startup may also be somewhat slow.

The login screen appears even if you usually login automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

Test while in safe mode. Same problem?

After testing, restart as usual (not in safe mode) and verify that you still have the problem. Post the results of the test.

I am having this issue as well, for one specific app, Tweedeck. I tried the above remedies without success, as well as the cache-emptying remedy posted elsewhere.

First it was the Tweetdeck update giving me the error in Software Update whenever I tried to install. When I couldn't fix it and all options failed, I tried deleting the app, in hopes of reinstalling from the Mac App Store, rather than updating. But I get the same error now from the install (vs. update).

I have tried multiple networks, multiple connection types on those networks (hard and wireless). Other apps from the App Store work fine. Only Tweedeck hates me.

I've also Repaired Disk Permissions, Repaired Disk, restarted in Safe Mode, deleting all App Store caches per instructions elsewhere, including additional support/settings files for Software Update and Mac App Store that were not suggested. It's just Tweetdeck that is having the problem. HELP? I'll post the cache cleaning suggestion when I find the link again.

Edit:

I also tried rebuilding the entire spotlight index, which didn't fix the issue.

The link I mentioned regarding the App Store cache is here:

http://www.cnet.com/news/fix-corrupt-mac-app-store-downloads/

I have also removed the following files to no avail:

~/Library/Caches/com.apple.storeagent/ (archived copy, deleted orig)

HD/Library/Updates/ (archived copy on desktop, orig contents deleted)

terminal: open $TMPDIR../C/

/com.apple.appstore (archived copy, deleted orig)

/com.apple.WebKit.WebContent+com.apple.appstore (archived copy, deleted orig)

After deleting and restarting, when I open Software Update, it still gives me the original error (see original poster), and it even remembers my "Updated in the last 30 days". So it STILL has a cache somewhere I am missing.

here is a pic

I have now:

-hidden the app in the app store "purchased" pane

-deleted all backup copies of the app on connected drives

-enabled debug menu for App Store (http://osxdaily.com/2011/01/10/enable-mac-app-store-debug-menu/)

-debug > clear cookies

-debug > reset app

-tried option-install in app store to reinstall (gives same error)

When I check console after failed install and dialogue box, I get:

7/31/15 1:18:56.573 AM storeagent[468]: *** Assertion failure in -[ISCheckPreflightOperation verifyDistributionAtURL:allowsDevSign:allowsUnsigned:osVersionToBeInstalled:err or:distributionController:], /SourceCache/Pisa/Pisa-232.11/ISCheckPreflightOperation.m:297

Any help?

I think I got it. Thanks to clues from: (https://gist.github.com/timsutton/9966396)

***Warning. This solved my unable to update/reinstall/install issue. However, it seems to have refreshed some incompatible updates and partial downloads in the Software Update app. I had 7 incompatible (Apple apps) before, now I have only 2, and the other 5 tried to download. I canceled, rather than overwrite my working Mavericks apps with non-working Yosemite versions,***

I made sure to have the outdated Tweetdeck app still available.

(previously I archived it and deleted the original, while trying to fix the main problem)

Close App Store app.

I went into ~/Library/Caches/

I archived a copy, then deleted the original of:

file "TweetdeckFast...

folder "storeagent"

folder "com.apple.storeagent"

folder "com.apple.storehelper"

I did a little overkill there, but i have no way of doing it over to narrow it down.

Empty Trash

A few subitems are still in use and will not be deleted. Delete everything you are allowed to.

Go into Activity Monitor > CPU pane

search by "store" in upper right field

select and force-quit the two active "store" items (named similar to archived and deleted files/folders above)

Empty Trash

Open App Store App

Click on suggested update in Software Update pane.

FINALLY WORKS