Mac Won T Install App

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This document is for the HP Smart app on Mac. If you are using a Windows 10 computer or an Android or Apple iOS mobile device, go to Install and Use the HP Smart App (Windows 10) or Install and Use the HP Smart App (Android, iOS).

File this one under “Obscure problems that could ruin your day.” TidBITS reader Randy Singer alerted us that due to an expired certificate, OS X installers downloaded prior to 14 February 2016 won’t work.


The Apple Worldwide Developer Relations Intermediate Certificate is required for all apps in the Mac App Store, including OS X installers. When used to sign an app, the certificate enables OS X to confirm that the app has not been corrupted or modified by an attacker. This certificate expired on 14 February 2016, causing error dialogs and preventing some apps from launching. Most affected apps have already been updated with the new certificate. But if youdownloaded an OS X installer in case of trouble, you may be in for a surprise the next time you try to use it.

Happily, this is an easy problem to fix ahead of time:

  1. Delete any old OS X installers in the Applications folder or in other locations (be sure to look on external hard drives too; if the App Store detects an old installer, it won’t let you get a new one). These installers have names like Install OS X El Capitan and Install OS X Yosemite.
  2. Open the App Store app by choosing Apple menu > App Store.

  3. Click the Purchased tab. Enter your App Store password if prompted.

  4. Scroll down to the OS X installer you want and click Download.


The new installers are signed with a certificate that expires on 7 February 2023, so it will be quite a few years before Mac users are affected again.

Those who have created any bootable install disks for OS X will need to recreate them with the new installers. Dan Frakes wrote a guide to creating OS X 10.11 El Capitan install disks for Macworld.

There is one qualification to all this. Apple won’t allow a newer Mac to download versions of OS X that aren’t compatible with that Mac, so on a 27-inch iMac with Retina display, for instance, the App Store app refuses to let you download Mac OS X 10.7 Lion.


If you are in the middle of an OS X install and get tripped up by the expired certificate, Randy Singer offers a suggestion on how you can work around the problem quickly, without having to download a new installer:

  1. In the OS X Installer, choose Utilities > Terminal.
  2. Enter sudo date 0201010116, press Return, and enter your password.
  3. Quit Terminal and continue the install.

That Terminal command sets your system date to 1 February 2016 — before the certificate’s expiration — so the installer can continue. Once you have completed the installation, visit System Preferences > Date & Time to reset the system date. Thanks to Randy for the heads up on this issue and the workaround!

As noted, this expired certificate affects more than just OS X installers — a number of Mac App Store apps suffered from it as well. If downloading a new version of an affected installer isn’t an option for some reason, Rich Trouton noted in 2012 that there’s an -allowUntrusted flag for the command line installer utility that might help, as might Greg Neagle’s flatpkgfixer.py tool.

As indicated by those posts from 2012, this is only the latest in a series of expired certificate snafus that have rendered Mac App Store apps unusable — the last one hit in November 2015 (see “The Mac App Store Is Breaking Apps,” 12 November 2015). Put bluntly, Apple needs to do a better job in managing its Worldwide Developer Relations Intermediate Certificate and alerting both users and developers to the implications of any expiration or revocation. Having this sort of sporadic failure is decidedly a strike against “It just works.”

Reinstall from macOS Recovery

macOS Recovery makes it easy to reinstall the Mac operating system, even if you need to erase your startup disk first. All you need is a connection to the Internet. If a wireless network is available, you can choose it from the Wi-Fi menu , which is also available in macOS Recovery.

1. Start up from macOS Recovery

To start up from macOS Recovery, turn on your Mac and immediately press and hold one of the following sets of keys on your keyboard. Release the keys when you see an Apple logo, spinning globe, or other startup screen.

Command (⌘)-R

Reinstall the latest macOS that was installed on your Mac (recommended).

Option-⌘-R

Upgrade to the latest macOS that is compatible with your Mac.

Shift-Option-⌘-R

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Reinstall the macOS that came with your Mac, or the closest version still available.

You might be prompted to enter a password, such as a firmware password or the password of a user who is an administrator of this Mac. Enter the requested password to continue.

Mac won

When you see the utilities window, you have started up from macOS Recovery.

2. Decide whether to erase (format) your disk

You probably don't need to erase, unless you're selling, trading in, or giving away your Mac, or you have an issue that requires you to erase. If you need to erase before installing macOS, select Disk Utility from the Utilities window, then click Continue. Learn more about when and how to erase.

3. Install macOS

When you're ready to reinstall macOS, choose Reinstall macOS from the Utilities window. Then click Continue and follow the onscreen instructions. You will be asked to choose a disk on which to install.

  • If the installer asks to unlock your disk, enter the password you use to log in to your Mac.
  • If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
  • If the installer is for a different version of macOS than you expected, learn about macOS Recovery exceptions.
  • If the installer offers you the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.

Please allow installation to complete without putting your Mac to sleep or closing its lid. During installation, your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.

If your Mac restarts to a setup assistant, but you're selling, trading in, or giving away your Mac, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.

macOS Recovery exceptions

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The version of macOS offered by macOS Recovery might vary in some cases:

  • If macOS Sierra 10.12.4 or later has never been installed on this Mac, Option-Command-R installs the macOS that came with your Mac, or the closest version still available. And Shift-Option-Command-R isn't available.
  • If you erased your entire disk instead of just the startup volume on that disk, macOS Recovery might offer only the macOS that came with your Mac, or the closest version still available. You can upgrade to a later version afterward.
  • If your Mac has the Apple T2 Security Chip and you never installed a macOS update, Option-Command-R installs the latest macOS that was installed on your Mac.
  • If you just had your Mac logic board replaced during a repair, macOS Recovery might offer only the latest macOS that is compatible with your Mac.

If you can't get macOS Recovery to offer the installer you want, you might be able to use one of the other ways to install macOS.

Other ways to install macOS

  • You can also install macOS from the App Store or Software Update preferences. If you can't install macOS Catalina, you might be able to install an earlier macOS, such as macOS Mojave, High Sierra, Sierra, El Capitan, or Yosemite.
  • Or create a bootable installer disk, then use that disk to install macOS on your Mac or another Mac.