This happens because Microsoft blocks some IP ranges from downloading the ISO directly.
As a workaround, please use the Media Creation Tool to download the ISO. You can download the Windows 11 Media Creation Tool (MCT) from this link:
https://go.microsoft.com/fwlink/?linkid=2156295
Note: If you are unable to download MCT, please use an alternative system.
Run MCT and choose the ISO option when prompted.