To get the latest features and maintain the security, stability, compatibility, and performance of your Mac, it's important to keep your software up to date. Apple recommends that you always use the latest macOS that is compatible with your Mac.

Re-enter the Apple Account. Several users find themselves in a hassle when they try to connect to. The Mac App Store was released on January 6, 2011, to the users of Mac OS X Snow Leopard during a free update. Over 1000 apps were introduced during the launch of the app store. In 2018, Apple introduced a revamped version of the Mac App Store with the update of its latest operating system macOS Mojave. Reasons a Mac Application Won't Start. If you've been running the app that won't start for a while successfully, and now it won't start, something changed. There's a chance a file became corrupt because of a system crash, or the app may need to be updated. It may be in conflict with another app, or its permissions or preferences file may have.

Learn how to upgrade to macOS Big Sur, the latest version of macOS.

Check compatibility

If a macOS installer can't be used on your Mac, the installer will let you know. For example, it might say that your Mac doesn't have enough free storage space for the installation, or that the installer is too old to be opened on this version of macOS.

If you want to check compatibility before downloading the installer, learn about the minimum requirements for macOS Catalina, Mojave, High Sierra, Sierra, El Capitan, or Yosemite. You can also check compatible operating systems on the product-ID page for MacBook Pro, MacBook Air, MacBook, iMac, Mac mini, or Mac Pro.

Make a backup

Before installing, it’s a good idea to back up your Mac. Time Machine makes it simple, and other backup methods are also available. Learn how to back up your Mac.

Download macOS

It takes time to download and install macOS, so make sure that you're plugged into AC power and have a reliable internet connection.

These installers from the App Store open automatically after you download them:

  • macOS Catalina 10.15 can upgrade Mojave, High Sierra, Sierra, El Capitan, Yosemite, Mavericks
  • macOS Mojave 10.14 can upgrade High Sierra, Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion
  • macOS High Sierra 10.13 can upgrade Sierra, El Capitan, Yosemite, Mavericks, Mountain Lion, Lion

Your web browser downloads the following older installers as a disk image named InstallOS.dmg or InstallMacOSX.dmg. Open the disk image, then open the .pkg installer inside the disk image. It installs an app named Install [Version Name]. Open that app from your Applications folder to begin installing the operating system.

Mac App Store Won't Let Me Sign In

  • macOS Sierra 10.12 can upgrade El Capitan, Yosemite, Mavericks, Mountain Lion, or Lion
  • OS X El Capitan 10.11 can upgrade Yosemite, Mavericks, Mountain Lion, Lion, or Snow Leopard
  • OS X Yosemite 10.10can upgrade Mavericks, Mountain Lion, Lion, or Snow Leopard
Mac

Install macOS

Follow the onscreen instructions in the installer. It might be easiest to begin installation in the evening so that it can complete overnight, if needed.

If the installer asks for permission to install a helper tool, enter the administrator name and password that you use to log in to your Mac, then click Add Helper.

Please allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac might restart, show a progress bar, or show a blank screen several times as it installs both macOS and related updates to your Mac firmware.

Learn more

You might also be able to use use macOS Recovery to reinstall the macOS you're using now, upgrade to the latest compatible macOS, or install the macOS that came with your Mac.

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.

App Store Apple

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.

  1. 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.

  2. Log out of the App Store on your Mac (Menu Bar > > App Store, then Store > Sign Out).

  3. Reboot your Mac.

  4. Reopen the App Store, and log back in with your Apple ID (Store > Sign In).

  5. 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.

Mac App Store Won't Open

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.

Mac App Store Won't Let Me Sign In

Last Modified: Mar 6, 2020