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 Mac App Store (from the menu bar, choose Store > Sign Out).
Reboot your Mac.
Log back in to the App Store (Store > Sign In), then switch to the Purchases tab and click the Install button next to the app name to reinstall. Clicking this link will take you directly to the Purchases tab.
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.