Failed to personalized the software update

Shofiul_ wrote:

https://discussions.apple.com/content/attachment/3d86a42d-ca14-4d84-ae6e-4ce65c9c168a

Getting this error when tried to update my old MacBook M2 Pro 2023.

This is happening after I transferred data of old MacBook to my new Mac mini m4.

How to fix it without resetting the new Mac mini? I can't even transfer data to the old because Mac mini is running on MacOS 26. And the old one is running on MacOS 15.6

[Edited by Moderator]

Boilerplate suggestion >> If an error occurred while updating or installing macOS - Apple Support

More suggestions which bear attention .

There are factors:

Some which are beyond your control and those which are totally under your control

Like poor Wifi connection

Slow wifi connection

Too many other people downloading at the same time and Apple  Servers are overloaded

Software on the computer interfering with the download process including AntiVirus Software

Notation: Disabling the AV Software may or may not solve the issue.

Removal of the AV Software may increase the chances of the download to perform as expected.

Running behind a VPN which may increase Packet losses or corruption of the download 

Turn off any Third Party Two Way Firewall and try again 

Best Results are via Ethernet Cable to Router

Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal 

Try Again using the Software Update Applet in System Preferences / Setting 

Worst case - Restart in Recovery Mode and choose Reinstall macOS. 

This in theory will pull the latest version of macOS this computer qualifies to run 

There can be various causes for the "Failed to personalize" error.

In the worst case, the issue might be the one described here.

TidBITS – Solving the macOS Installer’s “Failed to Personalize” Error with New Firmware