Can't Sign in to iCloud – "Verification Failed. An unknown error occurred."

Hi,

I’m using a MacBook Air (2020, Intel) and I recently reset the OS. Now when I try to sign in with my Apple ID to iCloud, I keep getting this error:

“Verification Failed. An unknown error occurred.”

I’ve already tried the following:

• Restarted the Mac
• Checked internet connection (Wi-Fi is working fine)
• Ensured date & time are set automatically
• Tried logging in from Safe Mode
• Tried another network
• Checked Apple’s System Status (everything seems fine)

Despite all that, the error keeps showing up. I can sign in to my Apple ID on other devices and on iCloud.com without any issues, so the Apple ID itself seems to be fine.

Any idea what might be causing this or how to fix it?

Thanks in advance!