From time to time, customers contact us about certain error messages they see when downloading our apps via the Mac App Store. Such error messages include “OmniFocus.app is damaged and can’t be opened. Delete OmniFocus.app and download it again from the App Store” or “This application can’t be verified.”
We’re always happy to assist as much as possible, but it’s important to understand that Mac App Store purchases and downloads are controlled exclusively by Apple. This means that we cannot directly fix or repair the damaged files which are causing these error messages.
With that said, here are some steps we’ve found that can help work around these error messages. We recommend you carry them out in the order we’ve posted them here.
Delete the app from your Mac via the Launchpad app. (In our experience, deleting is more effective than merely dragging it to the Trash or by other methods.) Within the Launchpad, click and hold on the app icon, then click the black “X” icon that appears.
Log out of the App Store on your Mac (Menu Bar > > App Store, then Store > Sign Out).
Reboot your Mac.
Reopen the App Store, and log back in with your Apple ID (Store > Sign In).
Click your account name or photo at the bottom of the sidebar to see your past purchases. Click the Install cloud icon under the app name to reinstall. More information about redownloading past purchases can be found on Apple’s Support Site here.
If this doesn’t help, we’ve also heard reports that this issue can be solved by temporarily creating a new administrator user account on your Mac. Log into that administrator account to install the app, then switch back to your primary account to use it. You can remove the temporary account once that’s sorted out!
If you’re still encountering difficulty downloading from the Mac App Store, Apple’s support channel will have the most insight into their systems so we recommend contacting them directly.