My MacBook Air won’t accept correct password nor Apple ID password.

Based on what you’re describing, this issue is most commonly caused by one of a few things: a corrupted local user account, a problem with the macOS keychain or login services, a temporary Apple ID authentication sync issue, or (less commonly) a software bug in macOS 15.0 affecting the login screen. The fact that it worked briefly and then stopped again strongly suggests the system is having trouble validating credentials locally rather than your passwords actually being wrong.

There are several ways to resolve this, depending on what you’re most comfortable trying first.

• The safest starting point is booting into macOS Recovery and using Reset Password from there, which rebuilds the local account credentials instead of relying on the normal login screen.
• If that doesn’t hold, the next option is creating a new temporary admin account in Recovery and migrating your data into it — this often fixes cases where the original profile has become corrupted.
• Finally, if the Mac still refuses to authenticate, reinstalling macOS (which keeps your data intact) usually corrects any system-level issues affecting login and Apple ID verification.

For the first option, how you get to the "Reset Password" option will depend on whether your Mac has an Intel or Silicon CPU.

Ref: If you forgot your Mac login password - Apple Support << This applies regardless of whether or not you didn't forget your login password.

Tesserax wrote:

[...]

• If that doesn’t hold, the next option is creating a new temporary admin account in Recovery and migrating your data into it — this often fixes cases where the original profile has become corrupted.

[...]

Hey there, Tesserax. I have a question about this particular option.

What is the best way to migrate the data from one user account to another on the same Mac?

I've been working with another user in a situation that might require this, but they have limited drive space so I suggested similar action using an external drive to transfer files to and then back, after they've made space available.

Mac unresponsive after update to Tahoe 26… - Apple Community

In particular I'd be concerned about file ownership and permissions.

Hmm. I believe the best way to migrate data between two user accounts on the same Mac—while preserving ownership and permissions—is to use Apple’s built-in tools rather than manual drag-and-drop. Migration Assistant is ideal if you can temporarily remove one account and re-import it into the other, but when both accounts must remain, a more controlled approach works better. Using an external drive is smart for space-constrained systems, especially if you copy data in chunks and verify permissions as you go.

Here’s my suggested steps that should work even with limited disk space and keeps permissions intact:

1. Log in to an admin account (not the source or destination user).
2. Connect the external drive formatted as APFS or Mac OS Extended.
3. Copy the source user’s home folder from `/Users/olduser` to the external drive using Finder or using this command in the Terminal: sudo ditto /Users/olduser /Volumes/External/olduser
4. Log in as the destination user and copy the data back to their home folder.
5. To fix ownership and permissions use these commands: sudo chown -R newuser:staff /Users/newuser & sudo chmod -R u+rwX /Users/newuser
6. Verify access to Documents, Desktop, Pictures, Mail, and any app-specific folders.

This approach should avoid the common permission issues you’d see with simple Finder copies and ensures the destination user truly owns the files.

As you know, if the goal is a full account replacement, Migration Assistant from a Time Machine backup or disk image of the old user is even cleaner.

Thanks, my friend! 🙏🏽

I'll pass this info along to the author of the other thread.

You're very welcome!