Mac Air M4 not updating to macOS 27

Because your MacBook Air M4 is still showing macOS 26.6 as up to date, use Terminal to determine whether macOS 27 is actually being offered to your Mac.

First run: softwareupdate -l

Then run: softwareupdate --list-full-installers

The first command only checks the regular software updates available to your Mac.

The second lists the full macOS installers currently available for your Mac model.

Neither command installs or changes anything.

Your Automatic Updates being OFF does not prevent you from running these commands or manually upgrading macOS.

Apple documents these Terminal commands here: How to download and install macOS

Paste the complete output of both commands here.

That will tell us whether macOS 27 is being offered to your M4 and what the next step should be.

Your M4 MacBook Air is compatible with macOS 27, so compatibility does not appear to be the problem. 

The more important point is that your Mac is running macOS 26.6 while Software Update says “Your Mac is up to date,” even though Apple currently lists macOS 26.7.1 as a later macOS 26 release. 

I would therefore investigate why the newer macOS 26 update is not being offered before focusing on the macOS 27 upGrade.

Start by checking the exact macOS version and build number under  >> About This Mac. 

Then we can determine why Software Update is not offering the applicable newer macOS 26 update. 

The “up to date” message by itself does not tell us why an update is not being offered.

It is also worth checking whether your Mac is enrolled in Mobile Device Management (MDM), such as Jamf or Microsoft Intune. 

MDM policies can affect how macOS updates are offered or installed, although finding an MDM profile would not, by itself, prove that it is causing the problem. 

Also check Beta Updates and any configuration profiles.

If none of those explain the situation, we can then look at things such as a VPN, network filter, security software, or another network configuration that might be interfering with Software Update.

Once we understand why the newer macOS 26 update is not  appearing, we can address why macOS 27 is not being offered. 

I would hold off on forcing the macOS 27 installation until we've clarified that.

Apple — Update macOS on Mac

Apple — Find out which macOS your Mac is using

Apple — Mac computers compatible with macOS Tahoe 26

Computers that are compatible with macOS 27 Golden Gate 

Given everything you have already established, I think DFU Revive is a reasonable next step, rather than continuing with repeated installation attempts or exploring increasingly speculative causes.

The installer consistently stops at PREFLIGHT_FDR_RECOVERY at 22%, you have  confirmed the installer itself is valid, you have about 123 GB of free space, and the logs you have examined do not reveal an obvious cause. 

Repeating the same installation is therefore unlikely to provide much additional information.

I would use DFU Revive first. Apple describes Revive as updating the Mac's firmware and Recovery environment without erasing your data. 

If Revive completes successfully, boot normally and try the macOS update again. Apple: How to revive or restore Mac firmware

If the update still fails afterward, or if Revive itself cannot complete, then DFU Restore becomes a more appropriate next step. 

Restore erases the Mac and reinstalls macOS, so I would not use it as the first option while the existing system and your data remain accessible.

This approach also avoids spending time trying to prove whether the existing sealed system volume is corrupted. 

A successful Revive would address the firmware/Recovery side of the update process without requiring you to erase the Mac.

So my recommendation is: DFU >> Revive >> boot normally >> attempt the macOS update once.

If that fails, reassess before proceeding to Restore.

updates are well updates

a full version upgrade is different

try

Update macOS on Mac - Apple Support

That is an important distinction. The problem is no longer downloading macOS 27; the failure is occurring during the actual installation.

The fact that the installer remains at “31 minutes remaining” while your installation log appears to stop around 22%suggests that the installer is getting stuck at a particular installation stage. However, I would not assume from 22% alone what the underlying cause is. Apple notes that macOS installation progress can pause for long periods, so the elapsed-time estimate by itself doesn't prove that the installation has failed. (Apple Support)

Since you have already identified a repeatable point in the installation log, the log is the most useful evidence now. Rather than immediately retrying the installation or erasing anything, I would first determine exactly what the installer was doing at 22%.

If you still have the Terminal output, please paste the last 30–50 lines immediately before and after the point where it reaches 22%. That should let us distinguish between things such as a disk/APFS problem, installer/package verification issue, firmware-related operation, or simply a long-running installation phase.

Also, don't erase the Mac or use Disk Utility to erase anything at this stage. Apple recommends checking/repairing the startup disk and, if necessary, installing from macOS Recovery for persistent installation failures; neither step requires erasing your personal data. (Apple Support)

Apple — If an error occurs while updating or installing macOS

Paste that section of your Terminal log here, and I can analyze the actual 22% failure rather than guessing at the cause.

I'm going through all this now. I'm still getting "Checking for updates" but what I learned in Terminal is it takes a long time to get results sometimes. I saw have MacOS27 then issued the OS command to install it and it felt like a long time (meaning I forgot about it running) then finally saw the msg that it was installed (Terminal). But even after doing a restart and a refresh of system settings, I saw a flash rectangular pop-up that it looked like Tahoe 27.2 was successfully installed except it's still showing 26.6.2 in info ... I'm obviously not stuck (?) but I'm still not there.

Admin: there are now two threads about this. I'm using title "MacBook Air software update stuck in a loop "Checking for updates" "