Can’t update Mac OS Big Sur – Download failed – The signed AP ticket could not be found

September 26, 2021

I don’t post a lot about computer issues and their solutions (after all, this is not a tech blog), but when I do, it’s because the solution is not readily available on a quick search. I want to post about this particular issue that may have you tearing out your hair, as I was tearing out mine working on it. If you just need the solution and don’t want to hear how or why, you can skip to the solution here.

The Problem: Can’t update Mac OS Big Sur

Back in April, I upgraded from a 2010 iMac to a refurbished 2019 Mac Mini. It came pre-loaded with Big Sur 11.1, and barely a month later, an update came out for Big Sur 11.3. The issue was, no matter what I did, I could not get the update to go through. It would download the whole thing without an issue, and then when it went into preparing the installation, it would hang, then error out with “Download failed… check your internet connection”.

I tried everything to clear this error: restarting, shutting down, a file system check (both through single user boot and Disk Utility), a fresh and new admin user account, resetting the PRAM, resetting the SMC, safe mode/safe boot, recovery mode, internet recovery mode, using terminal to run softwareupdate, connecting via ethernet, using someone else’s wifi, downloading the package in multiple ways… None of it worked.

The only way I got from 11.1 to 11.3 was taking it down to Apple. They tried it multiple times as well, and ended up completely flashing the drive and using a configuration tool, which then, and only then, did the update take. They assured me it was not likely to happen again but sure enough… it did.

When the Mac OS Big Sur 11.6 update rolled out I was wary of trying it, knowing I’d probably be packing up my machine and taking it down to Apple again. Sure enough, failure after failure, with a tech and then a senior advisor on the line, no one knew what to do here. The senior advisor and I took a break to try to let a different installer method run for Big Sur 11.6, but it didn’t work. I did a little footwork on my own.

One of the key errors I found in the installer log was “The signed AP ticket could not be found”, and I need to state that error here, because if you’re Googling for “The signed AP ticket could not be found”, you’ll find this post that may help you. This is exactly how I found the MacRumors post that had my solution.

The Solution: Clear out your hosts file

Remember how I said I had upgraded from a 2010 Mac to this one? Well, the migration was the problem. Back in 2010 we didn’t have T2 security chips. At some point, one of the OS X installations had placed in the hosts file a line for, and that was gumming up the works. Simply commenting out this line (or deleting it) freed up the whole process, and everything went smoothly. Since this is an OS file, it affects every user on the system.

You can find your hosts file under /private/etc/hosts. You will need to use Go To to get there, as the /private directory is hidden, or you will need to enable the viewing of hidden files (Command + shift + period). The hosts file itself is not editable where it is, but you can drag out a copy, edit that, save it, then drag that file into the directory. Mac OS will ask if you want to replace the hosts file – simply select yes. I didn’t even have to restart for it to start working, but you may want to just to be sure.

If you totally mess up your hosts file, here’s what the default hosts file should look like:

# Host Database
# localhost is used to configure the loopback interface
# when the system is booting. Do not change this entry.
##	     localhost	broadcasthost

::1		    localhost

I hope this helps someone keep from tearing their hair out… Even Apple simply had no idea about it!

Aimee Cozza is a freelance illustrator out of Southern New Hampshire. She graduated from the New Hampshire Institute of Art in 2012 with a bachelor’s degree in illustration. Since then, she has been working in a variety of ways completing various illustrations for clients, friends, and for herself.

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2 thoughts on “Can’t update Mac OS Big Sur – Download failed – The signed AP ticket could not be found”

  1. Just like you don’t post a lot, I post even less!! But thank you! This worked for my error when trying to upgrade to OS monterrey. Same deal; I was updating from an older backup on a new macbook pro.

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