MacOS 27.0.1 "Software Update Complete" screen appears every time I log in

The details provided so far do not identify the cause of the problem with certainty. 

The “Software Update Complete” screen is part of macOS Setup Assistant, but what stands out is that it appears again each time you log in, even after you have tried Disk Utility, Safe Mode, and reinstalling macOS. Apple — About Setup Assistant

The next thing I would check is what happens when you enter your Apple Account credentials on that screen. 

If the sign-in is accepted and you reach the desktop, go to System Settings >> Apple Account and confirm that you are signed in and that there are no outstanding setup requests. 

Then restart the Mac and see whether the screen comes back.

If it does, note whether the Apple Account sign-in actually completed, whether you saw any error message, and the exact wording of the screen. That information should help narrow down why Setup Assistant is being presented again.

If System Settings >> General >> Device Management is available, you can also check whether a configuration profile is installed, particularly if the Mac is owned or managed by an organization. Apple — Use configuration profiles on Mac

Since you have already reinstalled macOS 27.0.1 (26A434) without resolving the issue, 

I would hold off on another reinstall for now. 

If the Apple Account sign-in completes successfully but the same screen continues to appear after restarting, that would be useful information to give Apple Support along with the exact wording of the screen and the macOS build number.

Using the  Product Feedback - and make it known to Apple regarding this ongoing issue

Based on what you have already tried, I think contacting Apple Support is the right next step.

I would not keep repeating Disk Utility repairs, Safe Mode, or macOS reinstalls, since none has changed the behaviour.

What you have described also makes this look less like an iCloud sign-in problem. 

The Mac is not managed, the iCloud login appears to complete successfully, and iCloud shows as fully signed in afterward. 

Even choosing “Skip” closes the Assistant while leaving the account signed in.

This suggests that macOS is repeatedly treating the post-update Setup Assistant as incomplete and launching it again at login. 

The fact that reinstalling macOS did not resolve the problem supports that possibility.

When you contact Apple Support, I would describe it as a persistent post-update Setup Assistant loop occurring after updating to macOS 27.0.1 (26A434), rather than simply an iCloud login problem. I would also mention that reinstalling macOS did not resolve it.

At this point, Apple Support is probably better placed to determine what is causing the Assistant to be triggered repeatedly. 

I would avoid using Terminal commands simply to suppress the screen, since that could conceal the symptom without fixing its underlying cause.

bit_troupe wrote:

Today, I updated my MacOS version to 27.0.1 (26A434). Since then, every time I log in, the "Software Update Complete" screen appears, and requests that I log into my iCloud account.

Sounds like the process may need you to connect to your iCloud account. I don't use iCloud except for Contacts & Messages....I have avoided having my computer tied completely to my AppleID. However, I do know that even with my very limited use of my AppleID......macOS 26.x Tahoe kept insisting on a problem with my AppleID although everything seemed to be working at the time so I avoided "fixing" it. The Apple error message provided no details or explanation. I later found out Air Drop only worked in one direction so I finally went through with what macOS desired with my AppleID and it got rid of the error. Something wasn't quite syncing correctly or compatible behind the scenes.

Thanks for your response.

I can confirm (1) the computer is not managed, (2) logging into iCloud via the Assistant appears to be successful without any error messages, and (3) there appear to be no incomplete logins or errors after the user login process completes (upon reviewing the iCloud section in settings). Even if I select “skip” from the Assistant screen, my iCloud account is fully signed in once the Assistant closes; so, it is unclear what is triggering the Assistant to continue appearing at startup.

Sounds like my next step will be to submit this to Support for action.

Thank you for the assistance. I will reach out to Apple Support and report back on their response/solution.

bit_troupe wrote:

Thank you for the assistance. I will reach out to Apple Support and report back on their response/solution.

If your time permits, we would be most interested in the outcome 🤞

I've had the exact same issue and symptoms and have tried the exact same things to resolve it. It's been an issue since one of the MacOS 27 public betas. Still hasn't been resolved.