Cannot update to OSTahoe 26.6.2 on MacBook Air M5

Your MacBook Air M5 is compatible with macOS Tahoe, so the Mac model itself does not explain why System Settings reports that macOS 26.4.1 is current.

The important fact to establish is what Apple's Software Update service is currently offering specifically to your Mac.

The System Settings message alone does not tell us why 26.6.2 is not being offered.

Open Terminal (Applications >> Utilities >> Terminal) and run:

softwareupdate --list

This asks macOS to check Apple's software-update service for updates applicable to your Mac.

Then run:

softwareupdate --list-full-installers

This displays the full macOS installers that Apple's service reports as available to your Mac.

Don't install anything from Terminal at this stage.

Please paste the complete output from both commands here.

From that output, we can determine the next troubleshooting step without assuming the cause.

You can also try Apple's documented method of refreshing Software Update: open System Settings >> General >> Software Update and press Command-R to check again.

The key distinction is that we do not yet know why your Mac reports 26.4.1 as up to date. The Terminal results should give us additional evidence before we diagnose the cause.

To Manual download Tahoe 26.6.2

Use this Terminal

softwareupdate --fetch-full-installer --full-installer-version 26.6.2 

Yes, un-enrolling from Beta Testing is worth checking, especially because your --list-full-installers output includes a macOS 27 beta.

However, I would not say that the beta enrollment is causing your 26.6.2 problem.

We do not have evidence of that yet.

Apple's current instructions say that on macOS Ventura 13.4 or later, you can stop receiving beta updates by going to System Settings → General → Software Update >> Beta Updates >> Off.

Apple says that after turning beta updates off, the Mac remains on its current software and can install the next commercial macOS release when it becomes available. (Apple Beta Software Program)

What I would do in your situation

Before running Terminal commands to download 26.6.2, I would first check:

System Settings >> General >> Software Update

Look for: Beta Updates

If it is set to anything other than Off, change it to: Off

Then restart the Mac and check Software Update again.

This is a safe diagnostic step: you are not downgrading macOS or removing macOS. You are simply telling Software Update not to offer beta releases.

One important distinction

There are two separate things:

Turning off Beta Updates on the Mac

This stops the Mac from receiving future beta updates. Apple specifically documents this procedure. (Apple Beta Software Program)

Leaving the Apple Beta Software Program entirely

That is a separate action involving your Apple Account on Apple's Beta website. You do not necessarily need to do this just to stop beta updates on this Mac. (Apple Beta Software Program)

So I would not completely leave the Apple Beta Software Program yet.

I would first set Beta Updates → Off on the Mac.

And there is an interesting clue in your output

Your Mac is currently reporting: macOS 27 Golden Gate Beta Version: 27.0

while also reporting: macOS Tahoe Version: 26.6.2

That makes checking the Beta Updates setting particularly relevant.

But we should keep the conclusion appropriately cautious:

Your Mac appears to have access to both the Tahoe 26.6.2 full installer and a macOS 27 beta full installer. This makes it reasonable to check whether Beta Updates is enabled, but your current evidence does not establish that beta enrollment is preventing 26.6.2 from appearing in Software Update.

Is this Mac enrolled in the iOS 26 beta? If so, unenroll it by turning off beta updates, restart, and check again:

Unenroll Your Devices - Apple Beta