You haven't told us what browser you are using to download or what website you are using to download this ISO.
If you want a Windows ISO the best thing to do is go to this link:
Windows Iso Downloader Tool
Microsoft Windows and Office ISO Download Tool allows an easy and comfortable way to download genuine Windows 7, Windows 8.1 and Windows 10 disk images (ISO) directly from Microsoft’s servers, as well as Office 2010, Office 2013, Office 2016, Expression Studio and Office for Mac.
Download the Windows ISO Downloader to your desktop or someplace you can find it.
Launch, double click, run the Windows ISO Downloader (it doesn't install anything on your system) and then make your selections:
Make your selections and choose to save the ISO to someplace you can find it.
If you have problems with that tell us about the system you are using to download:
The Windows Edition and Service Pack
The browser you are using or which browsers you have tried that don't work
The antivirus/antimalware applications you have installed
The exact error message you see
If you get some errors it is helpful to include in your reply a screenshot of the error so we can see what you are seeing.
Reading this link will tell you how to do that:
This tool allows an easy and comfortable way to download genuine Windows 7, Windows 8.1 and Windows 10 disk images (ISO) directly from Microsoft's servers, as well as Office 2010, Office 2013, Office 2016, Office 2019, Expression Studio and Office for Mac.
In the past, Microsoft provided disk images for many of their products through their subcontractor 'Digital River'. These downloads were pulled in early 2014. Afterwards, Microsoft made a limited selection of downloads available on their TechBench site. Our tool is based on TechBench, and makes a range of hidden products available for download.
Download:Windows-ISO-Downloader.exe
Version: 8.15
Release Date: 1 June 2019
Requirements: Windows 7 or newer, .NET Framework 4.x, Internet Explorer 8 or newer.
Support: For any support issues, please use our support forum. Current bugs and issues are usually already addressed in the forum, and don't need to be raised by email or Facebook.
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Microsoft Windows Iso Downloader Tool
For some tips and tricks (re-arming, unlocking additional Windows 7 versions, alternative download options, generic product keys etc.), please refer to the other articles about Microsoft products.