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Unable to Boot up following upgrade of MacOS

Hi guys,

my MAC has been stuck for months failing to boot up with the following message:

MacBook Pro 15″, OS X 10.11

Posted on Oct 14, 2020 10:21 PM

Reply
Question marked as Top-ranking reply

Posted on Oct 15, 2020 12:05 AM

Almost exactly one year ago the certificates for several macOS's expired.

This look like you are trying to install an OS with an expired certificate.


Apple updated the certificates so you can download High Sierra again.

Open Safari and click on the link below, Firefox will not work,

How to upgrade to macOS High Sierra - Apple Support

Go to Section 4 and click on Get macOS High Sierra

you will be redirected to the App Store High Sierra page.

It should say Get or Download.

This will download Install High Sierra.app directly to your Applications

folder. Using that and Terminal you can create a bootable USB installer.

How to create a bootable installer for macOS – Apple Support


If the App Store says ‘Open’ then it is detecting a previous download of the install app

go to the Applications folder locate Install macOS High Sierra.app.

Move it to the Trash, empty the Trash.

Restart, click on the link again, the App Store should say ‘Get' or 'Download'.


If your mac has an operating system on it then you can just set the Date & Time

to a date before October 2019 and your older installer will install.

When installed you can then set the Date & Time back to todays date.



1 reply
Question marked as Top-ranking reply

Oct 15, 2020 12:05 AM in response to nabilweidi

Almost exactly one year ago the certificates for several macOS's expired.

This look like you are trying to install an OS with an expired certificate.


Apple updated the certificates so you can download High Sierra again.

Open Safari and click on the link below, Firefox will not work,

How to upgrade to macOS High Sierra - Apple Support

Go to Section 4 and click on Get macOS High Sierra

you will be redirected to the App Store High Sierra page.

It should say Get or Download.

This will download Install High Sierra.app directly to your Applications

folder. Using that and Terminal you can create a bootable USB installer.

How to create a bootable installer for macOS – Apple Support


If the App Store says ‘Open’ then it is detecting a previous download of the install app

go to the Applications folder locate Install macOS High Sierra.app.

Move it to the Trash, empty the Trash.

Restart, click on the link again, the App Store should say ‘Get' or 'Download'.


If your mac has an operating system on it then you can just set the Date & Time

to a date before October 2019 and your older installer will install.

When installed you can then set the Date & Time back to todays date.



Unable to Boot up following upgrade of MacOS

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