1
You can directly download the Windows 11 ISO from the Microsoft website using the bottom (3rd) option on this link
https://www.microsoft.com/en-us/software-download/windows11
2
If you see an error when you use the bottom third link on the Microsoft web page to directly download the Windows 11 ISO, then the best option is to use the middle 2nd link to download the Media Creation Tool, then open that tool and use that tool to create the Windows 11 ISO on your drive, not a bootable USB, that process should work to create the Windows 11 ISO.
3
If you are still unable to download the Windows 11 ISO, what language version of the Windows 11 ISO do you need.