"Failed to prepare the software update. Please try again."

[Le0M]

After macOS 27 download is complete, installation won't go through.

Here's my machine
MBP M1 2020 (regular).
Installed: macOS Tahoe 26.5.1
Space available on ssd: 70+ GB

Here's what I tried so far:
Restart the computer
Boot in Safe Mode and upgrade from there
Reset internet settings
Uninstalled VPN
Waited for 8 hours from macOS 27 release time

Still no luck.


Anyone else in my situation?
Any suggestions on how to proceed?

 

[psp123]

Try to boot into recovery mode and change "Reduced Security" to "Full Security" for Macintosh HD.

 

[Michaelhuisman]

After macOS 27 download is complete, installation won't go through.

Here's my machine
MBP M1 2020 (regular).
Installed: macOS Tahoe 26.5.1
Space available on ssd: 70+ GB

Here's what I tried so far:
Restart the computer
Boot in Safe Mode and upgrade from there
Reset internet settings
Uninstalled VPN
Waited for 8 hours from macOS 27 release time

Still no luck.


Anyone else in my situation?
Any suggestions on how to proceed?

same here. M3Max MBP with 64GB RAM and about 400GB free SSD (out of 4TB). Odd. All macOS updates this year required safe mode - as it would go all the way to the end, with "5 min remaining" and then error. Safe mode not being enough today - will try psp123's suggestion but would have to check if it's set to Reduced Security or not in the first place.

 

[Le0M]

Try to boot into recovery mode and change "Reduced Security" to "Full Security" for Macintosh HD.

Already switched to full security. Downloading OS right now. Let's see if it works this time 🤞🏻

 

[Le0M]

@psp123
It worked!
Writing you from macOS 27 😀

 

[Michaelhuisman]

same here. M3Max MBP with 64GB RAM and about 400GB free SSD (out of 4TB). Odd. All macOS updates this year required safe mode - as it would go all the way to the end, with "5 min remaining" and then error. Safe mode not being enough today - will try psp123's suggestion but would have to check if it's set to Reduced Security or not in the first place.

switching to Full Security worked. Now the question is why it was on "Reduced"? Some really small audio plugin developers don't notarize their plugins - maybe 5 or so that I use... but normally there's no way in heck that I'd reduce the standard security profile, so a bit surprised - will leave on Full and see what, if anything is broken. Hmmm...

 

[Le0M]

switching to Full Security worked. Now the question is why it was on "Reduced"? Some really small audio plugin developers don't notarize their plugins - maybe 5 or so that I use... but normally there's no way in heck that I'd reduce the standard security profile, so a bit surprised - will leave on Full and see what, if anything is broken. Hmmm...

Perhaps the reduced security is set by default.

 

[pollycat]

M2 Ultra Mac Studio
Having the same problem installing.
Tried the "Full Security" trick but didn't work.
Kind of stuck about what to try next.

UPDATE: Now it has worked. Not sure what made it go through this time.